The Blob

by Tommy on 5/06/2017
Orange Space Blob

Orange Space Blob

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Cosmic Inflation in a Nutshell – The Asymptotic Universe

by Tommy on 2/06/2017
The Asymptotic Universe

The Asymptotic Universe

Rant alert. I did this once before – Here.

Quantum Arithmetic Disproves Cosmic Naturalness Paradigm

I’m actually getting a little tired having to go over fundamentals like this.

Start with the equation x = 1/x. x2 = 1.

That’s a tautology, but it does set the origin to x = 1 not x = 0.

Now let’s move on to two dimensions and complex numbers and set y = 1/x.

Now we have at least e, π and 2, and rescaling the unit 2 triangle to unit area we get √2.

What I do is arbitrarily set the origin of this curve to the energy level of 109 to 1016 GeV.

I call that point the big bang, baryogenesis, axion production, fa or whatever else you care to.

What it is – the nearly scale invariant, nearly globally and locally flat universe in which we live.

Again, with a finite speed of light c and Planck unit of action h, something is gonna break.

Eventually. Sooner, or later.

In our case it was sooner.

Now I know what comes later.

Update: If there is even the slightest deviation of this function from x = y = 1, it fails to describe the universe and/or mathematics. That is, x or y ≠ 0 at y or x = ∞. The ‘geometry of information’.

So it’s easy to see that the universe is highly fine tuned in a very natural way.

Quantum arithmetic comes to the rescue once again.

Falsify or verify, it’s your choice.

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Time Reversal Invariant BCS-BEC Topological Superfluids

by Tommy on 30/05/2017

Here it comes, one way or another the nutshell will be cracked.

Time-reversal invariant topological superfluids in Bose-Fermi mixtures, Jonatan Melkær Midtgaard, Zhigang Wu and G. M. Bruun (29 May 2017)

A mixed dimensional system of fermions in two layers immersed in a Bose-Einstein condensate (BEC) is shown to be a promising setup to realise topological superfluids with time-reversal symmetry (TRS). The induced interaction between the fermions mediated by the BEC gives rise to a competition between p-wave pairing within each layer and s-wave pairing between the layers. When the layers are far apart, intra-layer pairing dominates and the system forms a topological superfluid either with or without TRS. With decreasing layer separation or increasing BEC coherence length, inter-layer pairing sets in. We show that this leads either to a second order transition breaking TRS where the edge modes gradually become gapped, or to a first order transition to a topologically trivial s-wave superfluid. Our results provide a realistic roadmap for experimentally realising a topological superfluid with TRS for the first time.

What usually happens though is that you end up breaking the nutcracker.

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Quark Gluon Plasmas Via Bose-Einstein Condensates

by Tommy on 29/05/2017

Here the very hot is unified with the very cold.

From cold Fermi fluids to the hot QGP, Marcus Bluhm and Thomas Schaefer, Presented by M. Bluhm at Critical Point and Onset of Deconfinement (CPOD) 2016 (24 May 2017)

Strongly coupled quantum fluids are found in different forms, including ultracold Fermi gases or tiny droplets of extremely hot Quark-Gluon Plasma. Although the systems differ in temperature by many orders of magnitude, they exhibit a similar almost inviscid fluid dynamical behavior. In this work, we summarize some of the recent theoretical developments toward better understanding this property in cold Fermi gases at and near unitarity.

When the universe cools, energy must be extracted.

And work must be done.

Life. It’s a gas.

Very exciting.

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First Principles Intrinsic ZT=2.15 Found in an Antimonene Layer

by Tommy on 27/05/2017

Bismuthene should be even better.

Excellent Thermoelectric Performance Predicted in Two-Dimensional Buckled Antimonene: a First-Principles Study, Kai-Xuan Chen, Shu-Shen Lyu, Xiao-Ming Wang, Yuan-Xiang Fu, Yi Heng and Dong-Chuan Mo, J. Phys. Chem. C (22 May 2017), DOI:10.1021/acs.jpcc.7b03129

Nowadays, new emerging two-dimensional (2D) materials have become a hot topic in the field of theoretical physics, material science and nanotechnology engineering due to their high surface area, planar structure and quantum confinement effect. Within two-dimensional framework, we systematically concentrate on the buckled and puckered systems consisting of the VA group elements (denoted as arsenene, antimonene and bismuthene). Among these studied systems, the buckled antimonene harbors a thermoelectric figure of merit (ZT) of 2.15 at room temperature. This is probably the highest value that has ever been reported in pristine 2D materials. By simple biaxial strain engineering, the ZT can even get enhanced to 2.9 under 3% tensile strain. The enhancement mainly results from both tuning the electronic structures and reducing the thermal conductance. This work predicts a new promising candidate in thermoelectric devices, based on the fact that buckled antimonene has been lately fabricated and proved to be stable at ambient conditions.

Bring it on.

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Gravitational Axion Grand Unification of QCD With Gravity

by Tommy on 26/05/2017

The gravitational axion QCD unification magnus opus of Giorgi Dvali.

Topological Origin of Chiral Symmetry Breaking in QCD and in Gravity, Gia Dvali (17 May 2017)

We show that the assumption of non-zero topological susceptibility of the vacuum in a fermion-free version of a theory, such as gravity or QCD, suffices to conclude the following: Once N massless fermion flavors are added to the theory, they break the chiral flavor symmetry dynamically, down to a subgroup that would be anomaly-free under gauging; In both theories, the pseudo-Goldstone corresponding to axial U(1)-symmetry becomes massive; In QCD as well as in gravity the massless fermions are eliminated from the low energy spectrum of the theory. All the above conclusions are reached without making an assumption about confinement. Some key methods of our approach are: Reformulation of topological susceptibility in the language of a three-form gauge theory; Utilization of gravity in the role of a spectator interaction for the chiral anomaly-matching in QCD; Gauging chiral symmetries and matching their anomalies using the spectator Green-Schwarz type axions. Our observations suggest that breaking of chiral symmetries in QCD and in gravity can be described in unified topological language, and seemingly-disconnected phenomena, such as, the generation of eta’-meson mass in QCD and breaking of global chiral symmetry by gravity may share a secret analogy. The described phenomenon may shed a new light – via contribution of micro black holes into the gravitational topological susceptibility of the vacuum – on incompatibility between black holes and global symmetries. It appears that explicit breaking is not the sole possibility, and like QCD, gravity may break global symmetries dynamically. As an useful byproduct, matching of gravitational anomalies provides a selection tool for compositeness, eliminating possibility of massless composite fermions where standard gauge anomaly matching would allow for their existence.

And just in the nick of time too. String theory only lives on the inside of a black hole, apparently.

The microscopic quantum black holes are the fluctuating quantum spacetime topolopgy.


An awesome paper title, no?

See also:

Nambu-Goldstone Effective Theory of Information at Quantum Criticality, Gia Dvali, Andre Franca, Cesar Gomez, Nico Wintergerst, Phys. Rev. D 92, 125002 (1 December 2015), doi:10.1103/PhysRevD.92.125002

We establish a fundamental connection between quantum criticality of a many-body system, such as Bose-Einstein condensates, and its capacity of information-storage and processing. For deriving the effective theory of modes in the vicinity of the quantum critical point we develop a new method by mapping a Bose-Einstein condensate of N-particles onto a sigma model with a continuous global (pseudo)symmetry that mixes bosons of different momenta. The Bogolyubov modes of the condensate are mapped onto the Goldstone modes of the sigma model, which become gapless at the critical point. These gapless Goldstone modes are the quantum carriers of information and entropy. Analyzing their effective theory, we observe the information-processing properties strikingly similar to the ones predicted by the black hole portrait. The energy cost per qubit of information-storage vanishes in the large-N limit and the total information-storage capacity increases with N either exponentially or as a power law. The longevity of information-storage also increases with N, whereas the scrambling time in the over-critical regime is controlled by the Lyapunov exponent and scales logarithmically with N. This connection reveals that the origin of black hole information storage lies in the quantum criticality of the graviton Bose-gas, and that much simpler systems that can be manufactured in table-top experiments can exhibit very similar information-processing dynamics.

So it appears now that I have come full circle with this.

My axion adventure is now officially over.

18 months from start to finish.

Up Next: The Resistance.

Update 1: I pulled this paper off Scholar because I don’t peruse HEP on the ArXiv.

Sabine Hossenfelder just blogged this today, which led me to her Aeon article on this subject.

Black Hole Computing, Sabine Hossenfelder, Aeon (31 March 2016)

Update 2: It’s going to take me quite a while to work through this material now that I am officially interested in these subjects. To recapitulate my axion adventure now that it’s officially finally over (pending microwave gravitational cosmic QCD axion detection in new and yet to be constructed sensitive cascading microwave axion haloscopes), this all began for me in the late fall of 2015 when I was distracted from my work in condensed matter physics – by the gravitational axion.

You can review those blog posts if you are feeling especially masochistic. Basically I had this wrapped up by Christmas of 2015, but being busy with other things and with raging dark matter and dark energy wars and an acrimonious election cycle – I had other responsibilities. So this whole idea languished until the election debacle, and it wasn’t until I could definitively exclude most, if not all, of the alternatives that I was anxious enough to get something written up on the axion and to my surprise, quantum cosmology. The origin of life essay was just practice for this.

On the Nature of Bismuth (I) Iodide in the Solid State

Thomas Lee Elifritz, Spec. Sci. Tech. 17, 85 (1994)

The Quantum Initiative – Energy in the 21st Century (1 January 2015)

Quantum Astrophysics – Quantum Physics and Astrophysics (8 October 2015)

The Cosmic Evolution of Autobiogenesis (12 June 2016)

Gravitational Axions as Dark Matter (1 January 2017)

Gravitational Axions in Quantum Gravity and Cosmology (8 January 2017)

My current status is that I am extremely pleased with my five self published 2015-2017 essays, and indeed with my 1994 bismuth iodide paper, and so considering recent developments and papers on these subjects I can’t see the need to continue to write about or even cover this stuff.

So welcome to the future! It’s here now.

And that future now is past.

I’ll see you in the future.

In Stockholm Sweden.

And the Planet Mars.

Update 3: Another big distraction for six months was the CERN LHC 750 GeV resonance.

I never drank the koolaide, though, being unqualified and unworthy.

Then the rocket blew up on the launch pad.

And then there was Trump.

Lizard King

Lizard King

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Rocket Lab Electron Launcher Launches at Exactly 4:20 PM

by Tommy on 25/05/2017
Rocket Lab Electron

Rocket Lab Electron

It didn’t quite make it to orbit, but it did everything else a rocket is supposed to do.

From my understanding it was only a test.

Congratulations, New Zealand!

And thank you, Rocket Lab.

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Chemical Bonding By Electronic Symmetry Breaking

by Tommy on 24/05/2017

This is a hugely important paper for me.

The chemical bond as an emergent phenomenon, Jon C. Golden, Vinh Ho and Vassiliy Lubchenko, The Journal of Chemical Physics, Vol. 146, 174502 (23 May 2017), DOI:10.1063/1.4982707

We first argue that the covalent bond and the various closed-shell interactions can be thought of as symmetry broken versions of one and the same interaction, viz., the multi-center bond. We use specially chosen molecular units to show that the symmetry breaking is controlled by density and electronegativity variation. We show that the bond order changes with bond deformation but in a step-like fashion, regions of near constancy separated by electronic localization transitions. These will often cause displacive transitions as well so that the bond strength, order, and length are established self-consistently. We further argue on the inherent relation of the covalent, closed-shell, and multi-center interactions with ionic and metallic bonding. All of these interactions can be viewed as distinct sectors on a phase diagram with density and electronegativity variation as control variables; the ionic and covalent/secondary sectors are associated with on-site and bond-order charge density wave respectively, the metallic sectorwith an electronic fluid. While displaying a contiguity at low densities, the metallic and ionic interactions represent distinct phases separated by discontinuous transitions at sufficiently high densities. Multi-center interactions emerge as a hybrid of the metallic and ionic bond that results from spatial coexistence of delocalized and localized electrons. In the present description, the issue of the stability of a compound is that of mutual miscibility of electronic fluids with distinct degrees of electron localization, supra-atomic ordering in complex inorganic compounds comes about naturally. The notions of electronic localization advanced hereby suggest a high throughput, automated procedure for screening candidate compounds and structures with regard to stability, without the need for computationally costly geometric optimization.

This is vindication enough for me.

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University of Illinois Covers the Dark Energy Survey DECam

by Tommy on 23/05/2017
Dark Energy Survey

Dark Energy Survey

This is really a must read student newspaper article on dark matter.

University astronomers unravel the universe with dark matter, Jean Kang, The Daily Illini, The Independent Student Newspaper at the University of Illinois since 1871 (22 May 2017)

This is exactly how science promotion should be done.

You can follow this up by reading the wiki article on the Dark Energy Survey.

The Dark Energy Survey Wikipedia Page

The Dark Energy Survey Website

Discussion: How to pronounce Illini. Say Ill – Lin(e) – I … Alumni.

I also have a Latin Chinese dictionary. Haha.

Beat that if you think you can!

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Did I Really Invent Modern Quantum Cosmology? Yes I did.

by Tommy on 20/05/2017

Like the term ‘autobiogenesis’, I did do a superficial search of the term ‘quantum cosmology’ after I coined it. It turned up in the modern era by a loop quantum gravity enthusiast, a theory (hypothesis) to which I do not subscribe. But looking back further I noticed that the ArXiv also has a General Relativity – Quantum Cosmology catagory (gr-qc) which seems to have been active as far back as 2002. Searching around, it seems to have been a fallout of this paper by David Wiltshire of the University of Adelaide and Canterbury, derived from as far back as 1995.

An introduction to quantum cosmology, D.L. Wiltshire, Published in “Cosmology: the Physics of the Universe”, Eds. B. Robson, N. Visvanathan and W.S. Woolcock (World Scientific, Singapore, 1996, pp 473-531) (3 September 2003)

This is an introductory set of lecture notes on quantum cosmology, given in 1995 to an audience with interests ranging from astronomy to particle physics. Topics covered: 1. Introduction: 1.1 Quantum cosmology and quantum gravity; 1.2 A brief history of quantum cosmology. 2. Hamiltonian formulation of general relativity: 2.1 The 3+1 decomposition; 2.2 The action. 3. Quantisation: 3.1 Superspace; 3.2 Canonical quantisation; 3.3 Path integral quantisation; 3.4 Minisuperspace; 3.5 The WKB approximation; 3.6 Probability measures; 3.7 Minisuperspace for the Friedmann universe with massive scalar field. 4. Boundary Conditions: 4.1 The no-boundary proposal; 4.2 The tunneling proposal. 5. The predictions of quantum cosmology: 5.1 The period of inflation; 5.2 The origin of density perturbations; 5.3 The arrow of time.

Note: These summer school lecture notes have been available for 5 years; but are being placed on the archive to make them more easily accessible.

See also: The Masters Thesis of Michael Patrick Cooke at Imperial College London

An Introduction to Quantum Cosmology, Michael Patrick Cooke, Master Thesis, Imperial College London (24 September 2010)

So this is really ‘old school’ quantum cosmology. What I did was port over the entire bulk of the machinery of the topological quantum field theory of condensed matter physics and dumped it into cosmology. And then I used that result to rediscover the cosmic QCD axion and then firmly established it as a microwave gravitational axion using that same mathematical machinery. But certainly Wiltshire’s exposition is useful as a historical starting point for this entirely new domain of quantum cosmology which has now been officially updated to these more modern standards.

Witness – the cosmic inflation war. I also notice David Wiltshire was an early proponent of inhomogeneous structure evolution as a basis for the mimicking of aspects of dark energy.

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Improved Water Electrolysis by Catalytic Electrodes Discovered

by Tommy on 20/05/2017

Iron phosphate on nickel phosphide foam. This does make some sense.

However, this is not catalysis. Even natural pH does not evolve oxygen or hydrogen.

This is more properly described as catalytic electrolysis since it involves using DC electricity.

Highly active catalyst derived from a 3D foam of Fe(PO3)2/Ni2P for extremely efficient water oxidation, Haiqing Zhoua, Fang Yua, Jingying Sun, Ran Hea, Shuo Chena, Ching-Wu Chua and Zhifeng Rena, PNAS (21 April 2017), doi:10.1073/pnas.1701562114

The oxygen evolution reaction (OER) is a sluggish reaction with poor catalytic efficiency, which is one of the major bottlenecks in realizing water splitting, CO2 reduction, and rechargeable metal–air batteries. In particular, the commercial utilization of water electrolyzers requires an exceptional electrocatalyst that has the capacity of delivering ultra-high oxidative current densities above 500 mA/cm2 at an overpotential below 300 mV with long-term durability. Few catalysts can satisfy such strict criteria. Here we report a promising oxygen-evolving catalyst with superior catalytic performance and long-term durability; to the best of our knowledge, it is one of the most active OER catalysts reported thus far that satisfies the criteria for large-scale commercialization of water–alkali electrolyzers.

Commercial hydrogen production by electrocatalytic water splitting will benefit from the realization of more efficient and less expensive catalysts compared with noble metal catalysts, especially for the oxygen evolution reaction, which requires a current density of 500 mA/cm2 at an overpotential below 300 mV with long-term stability. Here we report a robust oxygen-evolving electrocatalyst consisting of ferrous metaphosphate on self-supported conductive nickel foam that is commercially available in large scale. We find that this catalyst, which may be associated with the in situ generated nickel–iron oxide/hydroxide and iron oxyhydroxide catalysts at the surface, yields current densities of 10 mA/cm2 at an overpotential of 177 mV, 500 mA/cm2 at only 265 mV, and 1,705 mA/cm2 at 300 mV, with high durability in alkaline electrolyte of 1 M KOH even after 10,000 cycles, representing activity enhancement by a factor of 49 in boosting water oxidation at 300 mV relative to the state-of-the-art IrO2 catalyst.

If we could make potassium phosphate somehow with this process that would be excellent.

Electrocatalytic production of potassium phosphate and nitrate was my original goal with this.

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The Cosmological Constant is Quantum Vacuum Energy Density

by Tommy on 19/05/2017

And it self gravitates.

I haven’t really been too concerned about the dark energy problem since it is outside of my area of expertise and the majority of the matter is still missing. I can only claim the known microwave (cosmic QCD gravitational) axion for Vera Rubin and Helen Quinn. However, it appears now the obvious has been quantified. Or at least mathematicalized. Let’s just say it has been formalized.

I am now officially interested.

How the huge energy of quantum vacuum gravitates to drive the slow accelerating expansion of the Universe, Qingdi Wang, Zhen Zhu and William G. Unruh, Phys. Rev. D 95, 103504 (11 May 2017), doi:10.1103/PhysRevD.95.103504

We investigate the gravitational property of the quantum vacuum by treating its large energy density predicted by quantum field theory seriously and assuming that it does gravitate to obey the equivalence principle of general relativity. We find that the quantum vacuum would gravitate differently from what people previously thought. The consequence of this difference is an accelerating universe with a small Hubble expansion rate H ∝ Λe−βG√Λ → 0 instead of the previous prediction H = √8πGρvac/3 ∝ √GΛ2 → ∞ which was unbounded, as the high energy cutoff Λ is taken to infinity. In this sense, at least the “old” cosmological constant problem would be resolved. Moreover, it gives the observed slow rate of the accelerating expansion as Λ is taken to be some large value of the order of Planck energy or higher. This result suggests that there is no necessity to introduce the cosmological constant, which is required to be fine tuned to an accuracy of 10−120, or other forms of dark energy, which are required to have peculiar negative pressure, to explain the observed accelerating expansion of the Universe.

It looks like I called this correctly at the beginning of the year. So quantum cosmology it is.

Converting quantum vacuum energy into active matter is how it is most efficiently dissipated.

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Exact Mappings of Lattice Gauge Theories Formalized

by Tommy on 19/05/2017

This reminds me of Manuel de Llano’s formalization of aspects of BCS-BOSE (BCS-BEC).

This is modern physics in action. Enjoy!

Exact Boson-Fermion Duality on a 3D Euclidean Lattice, Jing-Yuan Chen, Jun Ho Son, Chao Wang and S. Raghu (16 May 2017)

The idea of statistical transmutation plays a crucial role in descriptions of the fractional quantum Hall effect. However, a recently conjectured duality between a critical boson and a massless 2-component Dirac fermion extends this notion to gapless systems. This duality may shed light on highly non-trivial problems such as the half-filled Landau level, the superconductor-insulator transition, and surface states of strongly coupled topological insulators. Although this boson-fermion duality has undergone many consistency checks, it has remained unproven. We describe the duality in a non-perturbative fashion using an exact UV mapping of partition functions on a 3D Euclidean lattice. Our approach is purely analytic and has the advantage of being simple and exact.

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Active Matter as a Generalization of Autobiogenesis

by Tommy on 18/05/2017

It’s officially impossible for me to continue to cover nightly Arxiv breakthroughs, being engaged for the last six months as Lizard King. Maybe I can get around to them next week, but this essay was the standout of the lot, and there were a lot of them breakthroughy enough for me to report.

Active matter, Sriram Ramaswamy, To appear in the STATPHYS26 Special Issue of JSTAT (17 May 2017)

The study of systems with sustained energy uptake and dissipation at the scale of the constituent particles is an area of central interest in nonequilibrium statistical physics. Identifying such systems as a distinct category — Active Matter — unifies our understanding of autonomous collective move- ment in the living world and in some surprising inanimate imitations. In this article I present the Active Matter framework, briefly recall some early work, review our recent results on single-particle and collective behaviour, including experiments on active granular monolayers, and discuss new directions for the future.

Yup. We’re blobs. Pretty stupid looking blobs by the looks of it. Maybe we can … evolve!

Selective breeding and genetic engineering doesn’t seem to be working out for us.

The Cosmic Evolution of Autobiogenesis

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ARPES BCS-BEC Crossover Transition – Fe(1+x)Se(x)Te(1-x)

by Tommy on 17/05/2017

Grok and you shall know.

Tuning across the BCS-BEC crossover in the multiband superconductor Fe1+ySexTe1−x : An angle-resolved photoemission study, S. Rinott, K.B. Chashka A. Ribak, E. D. L. Rienks A. Taleb-Ibrahimi, P. Le Fevre, F.Bertran, M. Randeria and A.Kanigel, Science Advances 3, 4, e1602372 (21 April 2017), doi:101126/sciadv.1602372

The crossover from Bardeen-Cooper-Schrieffer (BCS) superconductivity to Bose-Einstein condensation (BEC) is difficult to realize in quantum materials because, unlike in ultracold atoms, one cannot tune the pairing interaction. We realize the BCS-BEC crossover in a nearly compensated semimetal Fe1+ySexTe1−x by tuning the Fermi energy, ϵF, via chemical doping, which permits us to systematically change Δ/ϵF from 0.16 to 0.5 were Δ is the superconducting (SC) gap. We use angle-resolved photoemission spectroscopy to measure the Fermi energy, the SC gap and characteristic changes in the SC state electronic dispersion as the system evolves from a BCS to a BEC regime. Our results raise important questions about the crossover in multiband superconductors which go beyond those addressed in the context of cold atoms.

This is how it will be done from now on.

Got any other ideas? I can think of a few.

I completely failed to predict this in 1994.

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Nanoscopic Shiba Islands for Topological Circuit Manipulation

by Tommy on 17/05/2017

This is what I wanted to do with bismuth on nickel, but this is still shocking nevertheless.

Quantized charge transport in chiral Majorana edge modes, Stephan Rachel, Eric Mascot, Sagen Cocklin, Matthias Vojta and Dirk K. Morr (15 May 2017)

Majorana fermions can be realized as quasiparticles in topological superconductors, with potential applications in topological quantum computing. Recently, lattices of magnetic adatoms deposited on the surface of s-wave superconductors – Shiba lattices – have been proposed as a new platform for topological superconductivity. These systems possess the great advantage that they are accessible via scanning-probe techniques, and thus enable the local manipulation and detection of Majorana modes. Realizing quantum bits on this basis will rely on the creation of nanoscopic Shiba lattices, so-called Shiba islands. Here, we demonstrate that the topological Majorana edge modes of such islands display universal electronic and transport properties. Most remarkably, these Majorana modes possess a quantized charge conductance that is proportional to the topological Chern number, C, and carry a supercurrent whose chirality reflects the sign of C. These results establish nanoscopic Shiba islands as promising components in future topology-based devices.

So what’s the holdup?

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Generalized Lieb-Schultz-Mattis Theorems for SPT Phases

by Tommy on 16/05/2017

I feel a major generalization ‘coming on.

Lieb-Schultz-Mattis theorems for symmetry protected topological phases, Yuan-Ming Lu, AMS 1127-81-159 (12 May 2017)

The Lieb-Schultz-Mattis (LSM) theorem and its descendants represent a class of powerful no-go theorems that rule out any short-range-entangled (SRE) symmetric ground state irrespective of the specific Hamiltonian, based only on certain microscopic inputs such as symmetries and particle filling numbers. In this work, we introduce and prove a new class of LSM-type theorems, where any symmetry-allowed SRE ground state must be a symmetry-protected topological (SPT) phase with robust gapless edge states. The key ingredient is to replace the lattice translation symmetry in usual LSM theorems by magnetic translation symmetry. These theorems provide new insights into numerical models and experimental realizations of SPT phases in interacting bosons and fermions.

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Non-Equilibrium Irreversible Thermodynamics and Uncertainty

by Tommy on 12/05/2017

I’m always looking for new ways to look at non-equilibrium and irreversible thermodynamics.

A simple proof of the thermodynamic uncertainty relation, Changbong Hyeon and Wonseok Hwang (11 May 2017)

Using Brownian motion in periodic potential V(x) tilted by a force f, we prove the thermodynamic uncertainty relation, a recently conjectured principle for statistical errors and irreversible heat dissipation in nonequilibrium steady states. According to the relation, nonequilibrium output generated from dissipative processes necessarily incurs an energetic cost or heat dissipation q, and in order to limit the output fluctuation within a relative uncertainty ϵ, at least 2kBT2 of heat must be dissipated. We show that this bound is attained not only at near-equilibrium (fV′(x)) but also at far-from-equilibrium (fV′(x)), more generally when the dissipated heat is normally distributed. Furthermore, the energetic cost is maximized near the critical force when the barrier separating the potential wells is about to vanish. Our derivation of the uncertainty relation also recognizes a new bound of nonequilibrium dissipation that the variance of dissipated heat (σ2q) increases with its mean (μq) and is greater than 2kBTμq.

Thermodynamic uncertainty certainly is a new way of looking at these subjects.

This paper is as insightful as it gets.

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Quantum Anomaly Manifestation By Dimensional Reduction

by Tommy on 12/05/2017

This is how the quantum cosmology dark matter axion nutshell will be ultimately cracked.

Anomaly Manifestation of Lieb-Schultz-Mattis Theorem and Topological Phases, Gil Young Cho and Shinsei Ryu (10 May 2017)

The Lieb-Schultz-Mattis theorem constrains the possible low-energy and long-distance behaviors of states which emerge from microscopic lattice Hamiltonians. The theorem dictates that the emergent state cannot be a trivial symmetric insulator if the filling per unit cell is not integral and if lattice translation symmetry and particle number conservation are strictly imposed. Investigating one-dimensional symmetric gapless states which are forced to be critical by the theorem, we show that the theorem, the absence of a trivial insulator phase at non-integral filling, has a very close connection to quantum anomaly. We further show that, in terms of symmetry realizations on low-energy modes, low-energy spectrum, and anomaly, the gapless states emergent from lattice Hamiltonians are equivalent to the boundary theory of the strong symmetry-protected topological phases in one-higher dimensions, where non-local translational symmetry of the lattice is encoded as some local symmetry. Once a global symmetry is realized in a non-on-site fashion, the boundary of the topological phases can be realized in a stand-alone lattice model, and the no-go theorem for the boundary is circumvented, similar to the recent discussions of the half-filled Landau level and topological insulators. Finally we extend our analysis to the higher-dimensional example, the Dirac semimetal in three spatial dimensions.

See also:

Lieb-Schultz-Mattis Theorem and its generalizations from the Perspective of the Symmetry Protected Topological phase, Chao-Ming Jian, Zhen Bi and Cenke Xu (28 April 2017)

We ask whether a local Hamiltonian with a featureless (fully gapped and nondegenerate) ground state could exist in certain quantum spin systems. We address this question by mapping the vicinity of certain quantum critical point (or gapless phase) of the d−dimensional spin system under study to the boundary of a (d+1)−dimensional bulk state, and the lattice symmetry of the spin system acts as an on-site symmetry in the field theory that describes both the selected critical point of the spin system, and the corresponding boundary state of the (d+1)−dimensional bulk. If the symmetry action of the field theory is non-anomalous, i.e. the corresponding bulk state is a trivial state instead of a bosonic symmetry protected topological (SPT) state, then a featureless ground state of the spin system is allowed; if the corresponding bulk state is indeed a nontrivial SPT state, then it likely excludes the existence of a featureless ground state of the spin system. From this perspective we identify the spin systems with SU(N) and SO(N) symmetries on one, two and three dimensional lattices that permit a featureless ground state. We also verify our conclusions by other methods, including an explicit construction of these featureless spin states.

These are long and complicated papers with lots of references, so take your time.

Nevertheless, if you persist, you will get up to speed on this.

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Superuniversal Transport Near a Quantum Critical Point

by Tommy on 12/05/2017

This paper was difficult to get through but contained a surprise at the end.

Superuniversal transport near a (2+1)-dimensional quantum critical point, Félix Rose and Nicolas Dupuis (10 May 2017)

We compute the zero-temperature conductivity in the two-dimensional quantum O(N) model using a nonperturbative functional renormalization-group approach. At the quantum critical point we find a universal conductivity σ∗/σQ (with σQ=q2/h the quantum of conductance and q the charge) in reasonable quantitative agreement with quantum Monte Carlo simulations and conformal bootstrap results. In the ordered phase the conductivity tensor is defined, when N≥3, by two independent elements, σA(ω) and σB(ω), respectively associated to O(N) rotations which do and do not change the direction of the order parameter. Whereas σA(ω→0) corresponds to the response of a superfluid (or perfect inductance), the numerical solution of the flow equations shows that limω→0σB(ω)/σQ=σ∗B/σQ is a superuniversal (i.e. N-independent) constant. These numerical results, as well as the known exact value σ∗B/σQ=π/8 in the large-N limit, allow us to conjecture that σ∗B/σQ=π/8 holds for all values of N, a result that can be understood as a consequence of gauge invariance and asymptotic freedom of the Goldstone bosons in the low-energy limit.

This is a nightmare of html formatting so you’ll just have to read the paper like I did.

It will be well worth your time if you’re interested in this kind of thing. Like I am.

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Hydrogen Ionization in Cosmic Webs Probed By Quasar Light

by Tommy on 11/05/2017
Cosmic Web Void Filament Structure

Cosmic Web Void Filament Structure

I’m reduced to science reporting by blog, press release and main stream media.

This new science publishing paradigm is even catching up to Arxiv and Scholar.

University of California Santa Barbara Press Release

Measurement of the small-scale structure of the intergalactic medium using close quasar pairs, Alberto Rorai1, Joseph F. Hennawi, Jose Oñorbe, Martin White, J. Xavier Prochaska, Girish Kulkarni, Michael Walther, Zarija Lukić and Khee-Gan Lee, Science, 356, 6336, 418-422 (28 April 2017), DOI:10.1126/science.aaf9346

Space between galaxies is filled with a tenuous gas known as the intergalactic medium (IGM). The presence of hydrogen atoms in the IGM at different redshifts imprints a series of absorption lines in the spectra of background quasars. Rorai et al. studied pairs of closely spaced quasars and quantified how similar their absorption lines are as a function of transverse separation and redshift. They thus assessed the smoothness of the IGM on relatively small scales—several times the size of a galaxy. The results constrain interactions between galaxies and the IGM, such as heating by ultraviolet photons.

The distribution of diffuse gas in the intergalactic medium (IGM) imprints a series of hydrogen absorption lines on the spectra of distant background quasars known as the Lyman-α forest. Cosmological hydrodynamical simulations predict that IGM density fluctuations are suppressed below a characteristic scale where thermal pressure balances gravity. We measured this pressure-smoothing scale by quantifying absorption correlations in a sample of close quasar pairs. We compared our measurements to hydrodynamical simulations, where pressure smoothing is determined by the integrated thermal history of the IGM. Our findings are consistent with standard models for photoionization heating by the ultraviolet radiation backgrounds that reionized the universe.

Now Julie Cohen just needs to work on writing up the actual citation to the paper.

In addition to an embedded link, I’d like the cite.

Bad Julie! Very bad Julie!

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Cuprate Mottness Melted By Laser Charge Transfer Excitation

by Tommy on 10/05/2017

SISSA comes through for me again. Is there nothing these people can’t do?

Mottness at finite doping and charge instabilities in cuprates, S. Peli, S. Dal Conte, R. Comin, N. Nembrini, A. Ronchi, P. Abrami, F. Banfi, G. Ferrini, D. Brida, S. Lupi, M. Fabrizio, A. Damascelli, M. Capone, G. Cerullo and C. Giannetti, Nature Physics (8 May 2017), doi:10.1038/nphys4112

The influence of Mott physics on the doping–temperature phase diagram of copper oxides represents a major issue that is the subject of intense theoretical and experimental efforts. Here, we investigate the ultrafast electron dynamics in prototypical single-layer Bi-based cuprates at the energy scale of the O-2p → Cu-3d charge-transfer (CT) process. We demonstrate a clear evolution of the CT excitations from incoherent and localized, as in a Mott insulator, to coherent and delocalized, as in a conventional metal. This reorganization of the high-energy degrees of freedom occurs at the critical doping pcr ≈ 0.16 irrespective of the temperature, and it can be well described by dynamical mean-field theory calculations. We argue that the onset of low-temperature charge instabilities is the low-energy manifestation of the underlying Mottness that characterizes the p < pcr region of the phase diagram. This discovery sets a new framework for theories of charge order and low-temperature phases in underdoped copper oxides.

Massimo does know how to craft a proper press release.

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Room Temperature Biexcitons in Monolayer Tungsten Disulfide

by Tommy on 9/05/2017

This is like excitons in bismuth triiodide all over again.

Room temperature observation of biexcitons in exfoliated WS2 monolayers, I. Paradisanos, S. Germanis, N. T. Pelekanos, C. Fotakis, E. Kymakis, G. Kioseoglou and E. Stratakis (8 May 2017)

Single layers of WS2 are direct gap semiconductors with high photoluminescence (PL) yield holding great promise for emerging applications in optoelectronics. The spatial confinement in a 2D monolayer together with the weak dielectric screening lead to huge binding energies for the neutral excitons as well as other excitonic complexes, such as trions and biexcitons whose binding energies scale accordingly. Here, we report on the existence of biexcitons in mechanically exfoliated WS2 flakes from 78 K up to room temperature. Performing temperature and power dependent PL measurements, we identify the biexciton emission channel through the superlinear behavior of the integrated PL intensity as a function of the excitation power density. On the contrary, neutral and charged excitons show a linear to sublinear dependence in the whole temperature range. From the energy difference between the emission channels of the biexciton and neutral exciton, a biexciton binding energy of 65 – 70 meV is determined.

I am so excited, having experienced this phenomenon earlier. Much earlier.

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Lattice QCD Topology Further Refines Axion Mass Range

by Tommy on 9/05/2017

Topology (and axion’s properties) from lattice QCD with a dynamical charm, Florian Burger, Ernst-Michael Ilgenfritz, Maria Paola Lombardo, Michael Müller-Preussker and Anton Trunin, Proceedings of Quark Matter 2017 – XXVI International Conference on Ultrarelativistic Heavy-ion Collisions, February 5-11, 2017, Chicago IL (4 May 2017)

We present results on QCD with four dynamical flavors in the temperature range 0.9 ≲ T/Tc ≲ 2. We have performed lattice simulations with Wilson fermions at maximal twist and measured the topological charge with gluonic and fermionic methods. The topological charge distribution is studied by means of its cumulants, which encode relevant properties of the QCD axion, a plausible Dark Matter candidate. The topological susceptibility measured with the fermionic method exhibits a power-law decay for T/Tc ≳ 2, with an exponent close to the one predicted by the Dilute Instanton Gas Approximation (DIGA). Close to Tc the temperature dependent effective exponent approaches the DIGA result from above, in agreement with recent analytic calculations. These results constrain the axion window, once an assumption on the fraction of axions contributing to Dark Matter is made.

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First Light at the DESY XFEL Linear Free Electron X-Ray Laser

by Tommy on 5/05/2017
DESY XFEL Linear Superconducting Free Electron Laser

DESY XFEL Linear Superconducting Free Electron Laser

I had originally proposed one of these free electron lasers for the University of Wisconsin at Madison, under the umbrella of the Wisconsin Institute of Discovery. It was a colossal failure. Not only did the UW not get a free electron laser, but then the National Science Foundation and the Department of Energy canceled the Synchrotron Radiation Center in Stoughton, and the Wisconsin Institute of Discovery turned out to be the butt of jokes. That’s so sad, John D. Wiley.

First Light -The Firepower of the Idea – Light at the Foundation Of Discovery

We’ll just have to leave it to the Europeans again I guess.

European XFEL X-Ray Free Electron Laser

But all that empty farm land in Stoughton is making WARF rich.

And big buildings means big building contracts!

You can’t expect scientists to do things.

It’s all about patents now.

And big buildings.

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Gapless Symmetry Protected Topological Matter Proposed

by Tommy on 5/05/2017

After slugging through the previous paper, this was a breath of relief.

Gapless Symmetry Protected Topological Order, Thomas Scaffidi, Daniel E. Parker and Romain Vasseur (3 May 2017)

We introduce exactly solvable gapless quantum systems in d dimensions that support symmetry protected topological (SPT) edge modes. Our construction leads to long-range entangled, critical points or phases that can be interpreted as critical condensates of domain walls “decorated” with dimension (d−1) SPT systems. Using a combination of field theory and exact lattice results, we argue that such gapless SPT systems have symmetry-protected topological edge modes that can be either gapless or symmetry-broken, leading to unusual surface critical properties. Despite the absence of a bulk gap, these edge modes are robust against arbitrary symmetry-preserving local perturbations near the edges. In two dimensions, we construct wavefunctions that can also be interpreted as unusual quantum critical points with diffusive scaling in the bulk but ballistic edge dynamics.

Here, the method of their construction is useful. And the result is … interesting.

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Topological Quantum Chemistry Becomes Predictive

by Tommy on 5/05/2017

Wallpaper Fermions and the Topological Dirac Insulator, Benjamin J. Wieder, Barry Bradlyn, Zhijun Wang, Jennifer Cano, Youngkuk Kim, Hyeong-Seok D. Kim, A. M. Rappe, C. L. Kane and B. Andrei Bernevig, Submitted on March 21, 2017 (3 May 2017)

Recent developments in the relationship between bulk topology and surface crystalline symmetries have led to the discovery of materials whose gapless surface states are protected by crystal symmetries. In fact, there exists only a very limited set of possible surface crystal symmetries, captured by the 17 “wallpaper groups.” We show that all possible crystalline insulators, symmorphic and nonsymmorphic, can be exhaustively characterized by considering these groups. In particular, the two wallpaper groups with multiple glide lines, pgg and p4g, allow for a new topological insulating phase, whose surface spectrum consists of only a single, fourfold-degenerate, true Dirac fermion. Like the surface state of a conventional topological insulator, the surface Dirac fermion in this “topological Dirac insulator” provides a theoretical exception to a fermion doubling theorem. Unlike the surface state of a conventional topological insulator, it can be gapped into topologically distinct surface regions while keeping time-reversal symmetry, allowing for networks of topological surface quantum spin Hall domain walls. We report the theoretical discovery of new topological crystalline phases in the A2B3 family of materials in SG 127, finding that Sr2Pb3 hosts this new topological surface Dirac fermion. Furthermore, (100)-strained Au2Y3 and Hg2Sr3 host related topological surface hourglass fermions. We also report the presence of this new topological hourglass phase in Ba5In2Sb6 in SG 55. For orthorhombic space groups with two glides, we catalog all possible bulk topological phases by a consideration of the allowed non-abelian Wilson loop connectivities, and we develop topological invariants for these systems. Finally, we show how in a particular limit, these crystalline phases reduce to copies of the Su-Schrieffer-Heeger model.

See also:

Topological quantum chemistry, Barry Bradlyn, L. Elcoro, Jennifer Cano, M. G. Vergniory, Zhijun Wang, C. Felser, M. I. Aroyo and B. Andrei Bernevig (6 March 2017)

The past decade’s apparent success in predicting and experimentally discovering distinct classes of topological insulators (TIs) and semimetals masks a fundamental shortcoming: out of 200,000 stoichiometric compounds extant in material databases, only several hundred of them – a set essentially of measure zero – are topologically nontrivial. Are TIs that esoteric, or does this reflect a fundamental problem with the current piecemeal approach to finding them? Two fundamental shortcomings of the current approach are: the focus on delocalized Bloch wavefunctions – rather than the local, chemical bonding in materials – and a classification scheme based on a collection of seemingly unrelated topological indices. To remedy these issues, we propose a new and complete electronic band theory that assembles the last missing piece – the link between topology and local chemical bonding – with the conventional band theory of electrons. Topological Quantum Chemistry is a description of the universal global properties of all possible band structures and materials comprised of a graph theoretical description of momentum space and a dual group theoretical description in real space. This patches together local k⋅p dispersions into distinct global groups of energy bands: we classify all the possible bands for all 230 crystal symmetry groups involving s,p or d orbitals on any of the Wyckoff positions of every space group. We show how our topological band theory sheds new light on known TIs, and demonstrate the power of our method to predict a plethora of new TIs.

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Axions as Topological Inflatons and Geometric Curvatons

by Tommy on 5/05/2017
Axion Phase Diagram

Axion Phase Diagram

Back just before the first of the year I was deep into writing up my gravitational axion hypothesis. This was precipitated by new precision observational results demonstrating their particulate nature convincingly. The debate was raging between entropic gravity and fundamental particles, and to a lesser degree a wide variety of quite unreasonable proposals, and I was trying to get something together because I knew Vera Rubin was failing and the debate was reaching truly ridiculous and embarrassing proportions. Just as I was getting started, this paper showed up on the Arxiv. I already had a profound respect for SISSA, since their astronomy was crucial to the precision astronomical debates. So I was really happy to read this paper and blogged it briefly, but over the next week I was engaged in writing up my hypothesis and simply forgot all about it.

Since this has now been published in Physical Review Letters, it’s worth reviewing it here again.

Geometric Baryogenesis from Shift Symmetry, Andrea De Simone, Takeshi Kobayashi and Stefano Liberati, Phys. Rev. Lett. 118, 131101 (27 March 2017), doi:10.1103/PhysRevLett.118.131101

We present a new scenario for generating the baryon asymmetry of the universe that is induced by a Nambu-Goldstone (NG) boson. The shift symmetry naturally controls the operators in the theory, while allowing the NG boson to couple to the spacetime geometry. The cosmological background thus sources a coherent motion of the NG boson, which leads to baryogenesis. Good candidates of the baryon-generating NG boson are the QCD axion and axion-like fields. In these cases the axion induces baryogenesis in the early universe, and can also serve as dark matter in the late universe.

So this paper takes modern axion cosmological model building and then runs with it.

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Early Cosmological Axion Production Models Reconsidered

by Tommy on 4/05/2017

There is still considerable resistance to the axion hypothesis in the string theory community.

Axions, Instantons, and the Lattice, Michael Dine, Patrick Draper, Laurel Stephenson-Haskins and Di Xu (1 May 2017)

If the QCD axion is a significant component of dark matter, and if the universe was once hotter than a few hundred MeV, the axion relic abundance depends on the function χ(T), the temperature-dependent topological susceptibility. Uncertainties in this quantity induce uncertainties in the axion mass as a function of the relic density, or vice versa. At high temperatures, theoretical uncertainties enter through the dilute instanton gas computation, while in the intermediate and strong coupling regime, only lattice QCD can determine χ(T) precisely. We reassess the uncertainty on the instanton contribution, arguing that it amounts to less than a factor of 20 in χ at T = 1.5 GeV. We then combine the instanton uncertainty with a range of models for χ(T) at intermediate temperatures and determine the impact on the axion relic density. We find that for a given relic density and initial misalignment angle, the combined uncertainty amounts to a factor of 2-3 in the zero-temperature axion mass.

I’ll be the first to admit there may be an axion mass distribution with a long low mass tail.

So they can flail around all they want with this.

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Cubic Reference Lattice of Bismuth Superconductivity Proposed

by Tommy on 4/05/2017

It looks like somebody already beat me to it.

Theory of Ultra Low Tc Superconductivity in Bismuth: Tip of an Iceberg?, G. Baskaran (3 May 2017)

Superconductivity with an ultra low Tc ∼ 0.5 mK was discovered recently in bismuth, a semimetal. To develop a model and scenario for Bi we begin with a cubic reference lattice, close to A7 (dimerized cubic) structure of Bi. Three valence electrons hop among 6px, 6py and 6pz orbitals and form quasi one dimensional chains at half filling}. An interesting interplay follows: i) Mott localization tendency in the chains, ii) metallization by interchain hopping and iii) lattice dimerization by electron-phonon coupling. In our proposal, a potential high Tc superconductivity from RVB mechanism is lost in the game. However some superconducting fluctuations survive. Tiny fermi pockets seen in Bi are viewed as remnant evanescent Bogoliubov quasi particles} in an anomalous normal state. Multi band character admits possibility of PT violating chiral singlet superconductivity}. Bi has a strong spin orbit coupling; Kramers theorem protects our proposal for the bulk by replacing real spin by Kramer pair. Control of chain dimerization might resurrect high Tc superconductivity in Bi, Sb and As.

This far better than I could have done, a serious paper with a unique approach.

The problem is reconciling cubic with the trigonal mess.

This is coming whether you like it or not.

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Topoelectric RLC Circuit Simulation of Topological Semimetals

by Tommy on 3/05/2017

Topolectrical circuits, Ching Hua Lee and Ronny Thomale (2 May 2017)

First developed by Alessandra Volta and Felix Savary in the early 19th century, circuits consisting of resistor, inductor and capacitor (RLC) components are now omnipresent in modern technology. The behavior of an RLC circuit is governed by its circuit Laplacian, which is analogous to the Hamiltonian describing the energetics of a physical system. We show that “topolectrical” boundary resonances (TBRs) appear in the impedance read-out of a circuit whenever its Laplacian bandstructure resembles that of topological semimetals – materials with extensive degenerate edge modes known as Fermi arcs that also harbor enigmatic transport properties. Such TBRs not only provide unambiguous and highly robust signals for the presence of a topological phase, but also promise diverse applicability within high density electronic mode processing. Due to the versatility of electronic circuits, our topological semimetal construction can be generalized to topolectrical phases with any desired lattice symmetry, spatial dimension, and even quasiperiodicity. Topolectrical circuits establish a bridge between electrical engineering and topological states of matter, where the accessibility, scalability, and operability of electronics promises to synergize with the intricate boundary properties of topological phases.

There is not much that I can add to this, it seems seminal if it works.

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Quasi 1D Gapped Topological Surface States in Bi on InSb

by Tommy on 1/05/2017

I’ve been trying desperately to get back to my first true science love – bismuth.

It wasn’t my first science. It was the first where I could openly claim some fame.

And after all these years I am still trying to figure it all out, even as the expert on it.

Spin-polarized quasi 1D state with finite bandgap on the Bi/InSb(001) surface, J. Kishi, Y. Ohtsubo, K. Yaji, A. Harasawa, F. Komori, S. Shin, J. E. Rault, P. Le Fèvre, F. Bertran, A. Taleb-Ibrahimi, M. Nurmamat, H. Yamane, S. Ideta, K. Tanaka and S. Kimura (18 April 2017)

One-dimensional (1D) electronic states were discovered on 1D surface atomic structure of Bi fabricated on semiconductor InSb(001) substrates by angle-resolved photoelectron spectroscopy (ARPES). The 1D state showed steep, Dirac-cone-like dispersion along the 1D atomic structure with a finite direct bandgap opening as large as 150 meV. Moreover, spin-resolved ARPES revealed the spin polarization of the 1D unoccupied states as well as that of the occupied states, the orientation of which inverted depending on the wave vector direction parallel to the 1D array on the surface. These results reveal that a spin-polarized quasi-1D carrier was realized on the surface of 1D Bi with highly efficient backscattering suppression, showing promise for use in future spintronic and energy-saving devices.

And after 30 years it’s long past the time that I write up what I know about this subject again.

A whole bunch of metal chalcogenides keep stealing my fire.

I suppose I had better get started on it.

Update: I’m almost anxious enough to start. That’s really the only way I can write.

To your horror you can watch it online. It might not end up looking anything like this though.

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I Wear the Crown of Science

by Tommy on 29/04/2017

It’s official. Science is king and I’m the boss.

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Cosmic Microwave Background CMB Cold Spot Controversy

by Tommy on 28/04/2017

Even with all the recent post deletions, I seem to be stuck on post number 666. That’s very bad.

Since I am definitely afflicted with a very mild case of small positive integer factoring numerology neurosis (AKA Number Theory), that is an unacceptable situation to be in for very long. People might start to talk. Rumors may arise as to my true motivations. Therefore I recently ran across this. I was vaguely aware there was a minor temperature anomaly hidden in there but I never really researched it. So when it showed up in the popular press along with the multiverse mania I decided to investigate it. And then of course I had a crackpot idea. And crackpot ideas are meant to be shared. You never know what might come out of that. Certainly not the Multiverse.

Evidence against a supervoid causing the CMB Cold Spot, Ruari Mackenzie, Tom Shanks, Malcolm N. Bremer, Yan-Chuan Cai, Madusha L.P. Gunawardhana, András Kovács, Peder Norberg and Istvan Szapudi, Submitted to MNRAS (12 April 2017)

We report the results of the 2dF-VST ATLAS Cold Spot galaxy redshift survey (2CSz) based on imaging from VST ATLAS and spectroscopy from 2dF AAOmega over the core of the CMB Cold Spot. We sparsely surveyed the inner 5 radius of the Cold Spot to a limit of iAB ≤ 19.2, sampling ∼ 7000 galaxies at z < 0.4. We have found voids at z = 0.14, 0.26 and 0.30 but they are interspersed with small over-densities and the scale of these voids is insufficient to explain the Cold Spot through the ΛCDM ISW effect. Combining with previous data out to z ∼ 1, we conclude that the CMB Cold Spot could not have been imprinted by a void confined to the inner core of the Cold Spot. Additionally we find that our 'control' field GAMA G23 shows a similarity in its galaxy redshift distribution to the Cold Spot. Since the GAMA G23 line-of-sight shows no evidence of a CMB temperature decrement we conclude that the Cold Spot may have a primordial origin rather than being due to line-of-sight effects.

See also: An Alternative View

Could multiple voids explain the Cosmic Microwave Background Cold Spot anomaly, Krishna Naidoo, Aurélien Benoit-Lévy and Ofer Lahav, Mon Not R Astron Soc Lett 459 (1): L71-L75. (20 March 2016), DOI:10.1093/mnrasl/slw043

Understanding the observed Cold Spot (CS) (temperature of ~ -150 μK at its center) on the Cosmic Microwave Background (CMB) is an outstanding problem. Explanations vary from assuming it is just a > 3 sigma primordial Gaussian fluctuation to the imprint of a supervoid via the Integrated Sachs-Wolfe and Rees-Sciama (ISW+RS) effects. Since single spherical supervoids cannot account for the full profile, the ISW+RS of multiple line-of-sight voids is studied here to mimic the structure of the cosmic web. Two structure configurations are considered. The first, through simulations of 20 voids, produces a central mean temperature of ~ -50 μK. In this model the central CS temperature lies at ~ 2 sigma but fails to explain the CS hot ring. An alternative multi-void model (using more pronounced compensated voids) produces much smaller temperature profiles, but contains a prominent hot ring. Arrangements containing closely placed voids at low redshift are found to be particularly well suited to produce CS-like profiles. We then measure the significance of the CS if CS-like profiles (which are fitted to the ISW+RS of multi-void scenarios) are removed. The CS tension with the LCDM model can be reduced dramatically for an array of temperature profiles smaller than the CS itself.

So what is my crackpot theory? Sorry, I already killed it off. It’s not the multiverse, though.

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Emergent Metastable Order Through Topological Excitation

by Tommy on 27/04/2017

Besides having a Synchrotron Radiation Center in my back yard, and a world class research university in my front yard, Dragan Mihailovic was probably my biggest influence when I first became seriously interested in the spectroscopy of high temperature superconductivity.

Long range electronic order in a metastable state created by ultrafast topological transformation, Yaroslav A. Gerasimenko, Igor Vaskivskyi and Dragan Mihailovic (26 April 2017)

The fundamental idea that many body systems in complex materials may self-organise into long range order under highly non-equilibrium conditions leads to the notion that entirely new emergent states with new and unexpected functionalities might be created. In this paper we show for the first time that a complex metastable state with long range order can be created through a non-equilibrium topological transformation in a transition metal dichalcogenide. Combining ultrafast optical pulse excitation with orbitally-resolved large-area scanning tunnelling microscopy we find subtle, but unambiguous evidence for long range electronic order which is different from all other known states in the system, and whose complex domain structure is not random, but is described by harmonics of the underlying charge density wave order. We show that the structure of the state is topologically distinct from the ground state, elucidating the origins of its remarkable metastability. These fundamental insights on the mechanism open the way to in-situ engineering of the emergent properties of metastable materials with ultrafast laser pulses.

What a long and winding road it’s been.

Pumping and probing.

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Pressure Induced Superconductivity in Tantalum Ditelluride

by Tommy on 27/04/2017
Tantalum Ditelluride Phase Diagram

Tantalum Ditelluride Phase Diagram

Here is something interesting.

Separation of the charge density wave and superconducting states by an intermediate semimetal phase in pressurized TaTe2, Jing Guo, Huixia Luo, Huaixin Yang, Linlin Wei, Honghong Wang, Wei Yi, Yazhou Zhou, Zhe Wang, Shu Cai, Shan Zhang, Xiaodong Li, Yanchun Li, Jing Liu, Ke Yang, Aiguo Li, Jianqi Li, Qi Wu, Robert J Cava and Liling Sun (26 April 2017)

In layered transition metal dichalcogenides (LTMDCs) that display both charge density waves (CDWs) and superconductivity, the superconducting state generally emerges directly on suppression of the CDW state. Here, however, we report a different observation for pressurized TaTe2, a non-superconducting CDW-bearing LTMDC at ambient pressure. We find that a superconducting state does not occur in TaTe2 after the full suppression of its CDW state, which we observe at about 3 GPa, but, rather, a non-superconducting semimetal state is observed. At a higher pressure, ~ 21 GPa, where both the semimetal state and the corresponding positive magnetoresistance effect are destroyed, superconductivity finally emerges and remains present up to ~ 50 GPa, the high pressure limit of our measurements. Our pressure-temperature phase diagram for TaTe2 demonstrates that the CDW and the superconducting phases in TaTe2 do not directly transform one to the other, but rather are separated by a semimetal state, – the first experimental case where the CDW and superconducting states are separated by an intermediate phase in LTMDC systems.

I again remind my faithful readers that I utterly failed to predict this result way back in 1994.

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Chern Simons Theory of Composite Fermions Developed

by Tommy on 26/04/2017

This is how one begins to do quantum cosmology.

Chern-Simons Theory and Dynamics of Composite Fermions, Junren Shi (25 April 2017)

We propose a Chern-Simons field theoretical description of the fractional quantum Hall effect in 1+4 dimensions. It suggests that composite fermions reside on a momentum manifold with a nonzero Chern number. Based on derivations from microscopic wave functions, we further show that the momentum manifold has a uniformly distributed Berry curvature. As a result, composite fermions do not follow the ordinary Newtonian dynamics as commonly believed, but the more general symplectic one. For a Landau level with the particle-hole symmetry, the theory correctly predicts its Hall conductance at half-filling as well as the symmetry between an electron filling fraction and its hole counterpart.

If someone were to fund me, I might have time to do something about this problem.

Symplectic mechanics was something that I did study.

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Jarzynski Equality – Brownian Motion and Einstein Coefficients

by Tommy on 26/04/2017

Finally, here is the real deal. Fred Gittes is the next Udo Seifert.

Two famous results of Einstein derived from the Jarzynski equality, Fred Gittes, To Appear in Am. J. Phys (25 April 2017)

The Jarzynski equality (JE) is a remarkable statement relating transient irreversible processes to infinite-time free energy differences. Although twenty years old, the JE remains unfamiliar to many; nevertheless it is a robust and powerful law. We examine two of Einstein’s most simple and well-known discoveries, one classical and one quantum, and show how each of these follows from the JE. Our first example is Einstein’s relation between the drag and diffusion coefficients of a particle in Brownian motion. In this context we encounter a paradox in the macroscopic limit of the JE which is fascinating, but also warns us against using the JE too freely outside of the microscopic domain. Our second example is the equality of Einstein’s B coefficients for absorption and stimulated emission of quanta. Here resonant light does irreversible work on a sample, and the argument differs from Einstein’s equilibrium reasoning using the Planck black-body spectrum. We round out our examples with a brief derivation and discussion of Jarzynski’s remarkable equality.

Take your time with this, it’s an extremely difficult but interesting evolving subject.

Comments: This is a pedagogical paper

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Strongly Coupled P-Wave Superfluids May be Unstable

by Tommy on 26/04/2017

Ok, now I’m going to get into the good stuff. And the hard stuff. Pay attention!

Two-dimensional Fermi gases near a p-wave resonance, Shao-Jian Jiang and Fei Zhou (25 April 2017)

We study the stability of p-wave superfluidity for two-dimensional Fermi gases near a p-wave Feshbach resonance. A systematic analysis is carried out in the limit when the interchannel coupling is strong. We show that a homogeneous p-wave pairing is actually unstable due to quantum fluctuations, in contrast to the previously predicted p + ip superfluid in the weak-coupling limit [V. Gurarie et al., Phys. Rev. Lett. 94, 230403 (2005)]. This indicates an onset of instability at certain intermediate interchannel coupling strength. Alternatively, the instability can also be driven by lowering the particle density.

It’s not so much the results that they produce here but the techniques they use.

You can always work around or exploit instabilities.

That’s the whole point, right?

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Simple Clear Review Assessment of Thermoelectricity Science

by Tommy on 26/04/2017

Here is another great review I wish I had at my disposal 25 years ago now.

Thermoelectric Devices: Principles and Future Trends, Ibrahim M Abdel-Motaleb and Syed M. Qadri (25 April 2017)

The principles of the thermoelectric phenomenon, including Seebeck effect, Peltier effect, and Thomson effect are discussed. The dependence of the thermoelectric devices on the figure of merit, Seebeck coefficient, electrical conductivity, and thermal conductivity are explained in details. The paper provides an overview of the different types of thermoelectric materials, explains the techniques used to grow thin films for these materials, and discusses future research and development trends for this technology.

Again, well done, Sirs.

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Weyl Metals Reviewed

by Tommy on 26/04/2017

The gentleman has published a series of great reviews of these kinds of subjects.

Weyl Metals, A. A. Burkov, Submitted to Annual Reviews of Condensed Matter Physics (25 April 2017)

Weyl metal is the first example of a conducting material with a nontrivial electronic structure topology, making it distinct from an ordinary metal. Unlike in insulators, the nontrivial topology is not related to invariants, associated with completely filled bands, but with ones, associated with the Fermi surface. The Fermi surface of a topological metal consists of disconnected sheets, each enclosing a Weyl node, which is a point of contact between two nondegenerate bands. Such a point contact acts as a source of Berry curvature, or a magnetic monopole in momentum space. Its charge, or the flux of the Berry curvature through the enclosing Fermi surface sheet, is a topological invariant. We review the current state of this rapidly growing field, with a focus on bulk transport phenomena in topological metals.

The new quantum cosmology.

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Axion Physics Found In Dense QCD Equations of State

by Tommy on 26/04/2017

Since I’m on the subject, here is more on this remarkable region of quantum physics.

Anomalous Transport Properties of Dense QCD in a Magnetic Field, Vivian de la Incera (23 April 2017)

Despite recent advancements in the study and understanding of the phase diagram of strongly interacting matter, the region of high baryonic densities and low temperatures has remained difficult to reach in the lab. Things are expected to change with the planned HIC experiments at FAIR in Germany and NICA in Russia, which will open a window to the high-density-low-temperature segment of the QCD phase map, providing a unique opportunity to test the validity of model calculations that have predicted the formation of spatially inhomogeneous phases with broken chiral symmetry at intermediate-to-high densities. Such a density region is also especially relevant for the physics of neutron stars, as they have cores that can have several times the nuclear saturation density. On the other hand, strong magnetic fields, whose presence is fairly common in HIC and in neutron stars, can affect the properties of these exotic phases and lead to signatures potentially observable in these two settings. In this paper, I examine the anomalous transport properties produced by the spectral asymmetry of the lowest Landau level (LLL) in a QCD-inspired NJL model with a background magnetic field that exhibits chiral symmetry breaking at high density via the formation of a Dual Chiral Density Wave (DCDW) condensate. It turns out that in this model the electromagnetic interactions are described by the axion electrodynamics equations and there is a dissipationless Hall current.

Based on work done in collaboration with Efrain J Ferrer.

Well done, Sir and Madam.

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Dense Neutron Star Exotic Matter Simulated By Cold Atoms

by Tommy on 26/04/2017

Another round of super cold breakthroughs that I don’t have time or money to cover.

What can I do when I’ve already solved the major outstanding problems of our time?

Neutron Stars in the Laboratory, Vanessa Graber, Nils Andersson and Michael Hogg, Accepted for Publication in International Journal of Modern Physics D (1 March 2017)

Neutron stars are astrophysical laboratories of many extremes of physics. Their rich phenomenology provides insights into the state and composition of matter at densities which cannot be reached in terrestrial experiments. Since the core of a mature neutron star is expected to be dominated by superfluid and superconducting components, observations also probe the dynamics of large-scale quantum condensates. The testing and understanding of the relevant theory tends to focus on the interface between the astrophysics phenomenology and nuclear physics. The connections with low-temperature experiments tend to be ignored. However, there has been dramatic progress in understanding laboratory condensates (from the different phases of superfluid helium to the entire range of superconductors and cold atom condensates). In this review, we provide an overview of these developments, compare and contrast the mathematical descriptions of laboratory condensates and neutron stars and summarise the current experimental state-of-the-art. This discussion suggests novel ways that we may make progress in understanding neutron star physics using low-temperature laboratory experiments.

I could robotify or scriptify these posts, but then I wouldn’t have to actually read this stuff first.

I can safely say that I predicted this, though. And I can prove it!

Neutron stars are one step away from nothingness.

Failed nothings, they are. Like me.

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Happy Earth Day! Again.

by Tommy on 23/04/2017

Are we there yet?

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Efficient Exciton Plasmon Photo Emission and Absorption

by Tommy on 20/04/2017

It’s time to admit the exciton plasmon coupling era is upon us.

Proposal of highly efficient photoemitter with strong photon-harvesting capability and exciton superradiance, Takuya Matsuda and Hajime Ishihara (15 April 2017)

We propose a system of highly efficient photoemitters comprising metal-dielectric (plasmonic-excitonic) multilayered structures. In the proposed structure, the absorption in the excitonic layer is greatly enhanced through quantum interference between the split modes arising from the coupling of the layered excitons and the plasmons sustained by the metallic layer. Furthermore, the large interaction volume between surface plasmons and excitons causes exciton superradiance, which results in the extremely efficient photoemission. This finding indicates the possibility of designing highly efficient photoemitters based on simple layered structures.

So what is not to like about this?

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New Giant Planar Hall Effect Signals Axial Anomaly Presence

by Tommy on 20/04/2017

Lars Onsagar would love chemical physics right now.

Giant Planar Hall Effect in Topological Metals, A. A. Burkov (18 April 2017)

Much excitement has been generated recently by the experimental observation of the chiral anomaly in condensed matter physics. This manifests as strong negative longitudinal magnetoresistance and has so far been clearly observed in Na3Bi, ZrTe5 and GdPtBi. In this work we point out that the chiral anomaly must lead to another effect in topological metals, that has been overlooked so far: Giant Planar Hall Effect (GPHE), which is the appearance of a large transverse voltage when the in plane magnetic field is not aligned with the current. Moreover, we demonstrate that the GPHE is closely related to the angular narrowing of the negative longitudinal magnetoresistance signal, observed experimentally.

I had blogged Mr. Burkov earlier, he knows what he’s talking about.

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The Trump Russia Dossier

by Tommy on 19/04/2017
Trump Russia Dossier

Trump Russia Dossier

Happy 420 Day!

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MADMAX Dark Matter Axion Haloscope White Paper Released

by Tommy on 18/04/2017

There were quite a few breakthroughs on the ArXiV last night, which I don’t have time to cover right now, but I found this axion haloscope white paper on Scholar that needs to be fast tracked. You know, because of ‘gravitational axions’.

A new experimental approach to probe QCD Axion Dark Matter in the mass range above 40μeV, P. Brun, A. Caldwell, L. Chevalier, G. Dvali, E. Garutti, C. Gooch, A. Hambarzumjan, S. Knirck, M. Kramer, H. Kruger, T. Lasserre, A. Lindner, B. Majorovits C. Martens, A. Millar, G. Raffelt, J. Redondo , O. Reimann, A. Schmidt, F. Simon, F. Steffen, G. Wieching, The MADMAX Interest Group (20 March 2017)

Axions represent a class of particles that emerge in theoretical models explaining several mysteries of high-energy particle physics and cosmology. They explain the absence of CP violation in the strong interaction, provide dark matter candidates, and can be responsible for inflation and structure formation in the early universe. Several searches for axions and axion-like particles have constrained the parameter space over the last decades, however, no hints of axions have been found. The mass range of 1–1000 μeV remains highly attractive and well motivated region for dark matter axions. In this white paper we present a description of a new experiment based on the concept of a dielectric haloscope for the search for dark matter axions in the mass range 40–400 μeV. The experiment, called MADMAX, will consist of several parallel dielectric layers, whose separations can be adjusted and are placed in a strong magnetic field. This would lead to the emission of axion induced electromagnetic waves in the 10–100 GHz domain, with the frequency given by the axion mass.

Now all I have to do is read this white paper.

The race to the gravitational axion is on!

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High Mass-Energy Axions Excluded by LUX WIMP Search

by Tommy on 14/04/2017

I didn’t realize they would try this but I guess it’s a no brainer

I’m not listing all of the damn authors here though.

First searches for axions and axion-like particles with the LUX experiment, D.S. Akerib, et al., The LUX Collaboration, (7 April 2017)

The first searches for axions and axion-like particles with the Large Underground Xenon (LUX) experiment are presented. Under the assumption of an axio-electric interaction in xenon, the coupling constant between axions and electrons, gAe is tested, using data collected in 2013 with an exposure totalling 95 live-days × 118 kg. A double-sided, profile likelihood ratio statistic test excludes gAe larger than 3.5 × 10−12 (90% C.L.) for solar axions. Assuming the DFSZ theoretical description, the upper limit in coupling corresponds to an upper limit on axion mass of 0.12 eV/c2, while for the KSVZ description masses above 36.6 eV/c2 are excluded. For galactic axion-like particles, values of gAe larger than 4.2 × 10−13 are excluded for particle masses in the range 1-16 keV/c2. These are the most stringent constraints to date for these interactions.

I like my gravitational axions better, obviously, but they do have a good explanation of axions.

Our axions in this universe just happen to be super cool axions.

So what’s not to like about that? We’re so special.

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Proto Autobiogenesis on the Saturn Ice Moon World Enceladus

by Tommy on 13/04/2017
Saturn Ice Moon World Enceladus

Saturn Ice Moon World Enceladus

I don’t have even a link yet but this will make my blob look better anyways.

That had to be the most painful NASA press conference I ever had to shut right off. Cringeful.

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Dark Matter Cosmic Web Void Filament Imaging Refined

by Tommy on 12/04/2017
Galactic Dark Matter Halo Filaments

Galactic Dark Matter Halo Filaments

Particulate dark matter seems to be confirmed now.

I can only suggest that the gravitational axion detection will happen soon.

The weak-lensing masses of filaments between luminous red galaxies, Seth D. Epps and Michael J. Hudson, Monthly Notices of the Royak Astronomical Society, MNRAS, 468 (3): 2605-2613 (1 Narch 2017), DOI:10.1093/mnras/stx517

In the standard model of non-linear structure formation, a cosmic web of dark-matter-dominated filaments connects dark matter haloes. In this paper, we stack the weak lensing signal of an ensemble of filaments between groups and clusters of galaxies. Specifically, we detect the weak lensing signal, using CFHTLenS galaxy ellipticities, from stacked filaments between Sloan Digital Sky Survey (SDSS)-III/Baryon Oscillation Spectroscopic Survey luminous red galaxies (LRGs). As a control, we compare the physical LRG pairs with projected LRG pairs that are more widely separated in redshift space. We detect the excess filament mass density in the projected pairs at the 5σ level, finding a mass of (1.6 ± 0.3) × 1013 M for a stacked filament region 7.1 h−1 Mpc long and 2.5 h−1 Mpc wide. This filament signal is compared with a model based on the three-point galaxy–galaxy-convergence correlation function, as developed in Clampitt et al., yielding reasonable agreement.

I can comment where this is going though. Although I am not convinced yet either way about sub-horizon (dark energy) inhomogenieties, it’s clear the baryons are migrating into the dark matter filaments (I guess that’s standard terminology now), and the cosmic webs and voids are indeed inhomogenieties looking very much like a nanoscale (or in our case, megascale) phase separation into bosonic remnants of a node-line-sheet structure – which very much looks like domain wall disintegration and dissipation. Therefore the ‘gravitational axion’ paradigm I have proposed at the first of the year still holds. In my opinion, it firmly holds, and quite honestly the hypothesis is the last man standing, irrespective of the actual composite nature or structure of the bosons and/or excitons making up the dark matter. It still could be anything, but clearly this goes well beyond sterile QCD axions in my humble opinion. But alas, I would still take a sterile axion if that turns out to be the case. I’m very flexible with this as long as progress continues to be made. I’m looking for absolute exclusion of low scale SUSY, WIMPS and MACHOs, MOGs entropic gravity, although MACHOs are done and I still believe there is room for entropic gravity.

Somewhere. Over the rainbow. That’s it. I feel another song comin on … You know the story.

Rest in peace, Vera Rubin. 1928-2016.

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Collective Modes by Higgs’ Mechanism Obey Nambu’s Identity

by Tommy on 11/04/2017

This is a real eye opener.

Nambu identity and collective modes in superconductors and superfluid 3He, Gavriil Shchedrin and David M. Lee (7 April 2017)

Collective modes manifest themselves in a variety of different physical systems ranging from superconductors to superfluid 3He. The collective modes are generated via the Higgs-Anderson mechanism that is based on the symmetry breaking double well potential. Recently collective modes were explored in superconducting NbN and InO in the presence of a strong terahertz laser field. In both cases a single collective mode that oscillates with twice the frequency of the superconducting energy gap Δ was discovered. Superfluid 3He is the host for a whole variety of collective modes. In particular, in the superfluid 3He B-phase, two massive collective modes were found with masses √8̅/̅5̅ Δ and √1̅2̅/̅5̅ Δ. We show that for both cases of the superconducting films and for the superfluid 3He B-phase, the collective modes satisfy the Nambu identity that relates the masses of different collective modes to the energy gap parameter Δ.

This paper is mathematical elegance, personified.

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Exciton Plasmon Coupling Found in Tungsten Dichalcogenides

by Tommy on 10/04/2017

This is something you’ll definitely want for your superconducting plasma warp core.

Marrying excitons and plasmons in monolayer transition-metal dichalcogenides, Dinh Van Tuan, Benedikt Scharf, Igor Žutić and Hanan Dery (6 April 2017)

Just as photons are the quanta of light, plasmons are the quanta of orchestrated charge-density oscillations in conducting media. Plasmon phenomena in normal metals, superconductors and doped semiconductors are often driven by long-wavelength Coulomb interactions. However, in crystals whose Fermi surface is comprised of disconnected pockets in the Brillouin zone, collective electron excitations can also attain a shortwave component when electrons transition between these pockets. Here, we show that the band structure of monolayer transition-metal dichalcogenides gives rise to an intriguing mechanism through which shortwave plasmons are paired up with excitons. The coupling elucidates the origin for the optical side band that is observed repeatedly in monolayers of WSe2 and WS2 but not understood. The theory makes it clear why exciton-plasmon coupling has the right conditions to manifest itself distinctly only in the optical spectra of electron-doped tungsten-based monolayers.

It sounds like a marriage made in hell.

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Yakutite Nanodiamond is Impact Ejecta from the Popigai Crater

by Tommy on 10/04/2017

There is a bit more to report on the ongoing lonsdaleite saga. It’s not quite a war. Yet. But close.

Mineralogical and crystallographic features of polycrystalline yakutite diamond, Hiroaki Ohfuji, Motosuke Nakaya, Alexander P. Yelissevev, Valentin P. Afanasiev and Konstantin D. Litasov, Journal of Mineralogical and Petrological Sciences, 112, 46-51 (1 February 2017), doi:10.2465/jmps.160719g

This study revealed for the first time the microtexture and crystallographic features of natural polycrystalline diamond, yakutite found in placer deposits in the Siberian Platform, Russia. Yakutite consists of well–sintered nanocrystalline (5–50 nm) diamond and small amount of lonsdaleite showing distinct preferred orientations. Micro–focus X–ray and electron diffractions showed a coaxial relationship between lonsdaleite 100 and diamond 111, suggesting the martensitic formation of yakutite from crystalline graphite. These textural and crystallographic features are well comparable to those of the impact diamonds from the Popigai crater located in the central Siberia and strongly support the idea that yakutite is a product of long–distance outburst from the Popigai crater, which has been inferred merely from the geochemical signatures.

See also:

Investigation on the formation of lonsdaleite from graphite, V. A. Greshnyakov and E. A. Belenkov, Journal of Experimental and Theoretical Physics, 124, 2, 265–274 (23 March 2017), DOI:10.1134/S1063776117010125

Structural stability and the possible pathways to experimental formation of lonsdaleite—a hexagonal 2H polytype of diamond—have been studied in the framework of the density functional theory (DFT). It is established that the structural transformation of orthorhombic Cmmm graphite to 2H polytype of diamond must take place at a pressure of 61 GPa, while the formation of lonsdaleite from hexagonal P6/mmm graphite must take place at 56 GPa. The minimum potential barrier height separating the 2H polytype state from graphite is only 0.003 eV/atom smaller than that for the cubic diamond. The high potential barrier is indicative of the possibility of stable existence of the hexagonal diamond under normal conditions. In this work, we have also analyzed the X-ray diffraction and electron-microscopic data available for nanodiamonds found in meteorite impact craters in search for the presence of hexagonal diamond. Results of this analysis showed that pure 3C and 2H polytypes are not contained in the carbon materials of impact origin, the structure of nanocrystals found representing diamonds with randomly packed layers. The term “lonsdaleite,” used to denote carbon materials found in meteorite impact craters and diamond crystals with 2H polytype structure, is rather ambiguous, since no pure hexagonal diamond has been identified in carbon phases found at meteorite fall sites.

So lonsdaleite lives! But only fleetingly in impact nanodiamonds.

Shear strain is still the key to making lonsdaleite.

Exploding missiles is not the best way.

It takes nuance and finesse.

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Heavy Particle Beyond Standard Model Physics Is Limited

by Tommy on 8/04/2017

This should give any MACHO WIMPS pause for thought.

Pulsar Timing Constraints on Physics Beyond the Standard Model, Niayesh Afshordi, Hyungjin Kim and Elliot Nelson (15 March 2017)

We argue that massive quantum fields source low-frequency long-wavelength metric fluctuations through the quantum fluctuations of their stress-energy, given reasonable assumptions about the analytic structure of its correlators. This can be traced back to the non-local nature of the gauge symmetry in General Relativity, which prevents an efficient screening of UV scales (what we call the cosmological non-constant problem). We define a covariant and gauge-invariant observable which probes line-of-sight spacetime curvature fluctuations on an observer’s past lightcone, and show that current pulsar timing data constrains any massive particle to m ≲ 600 GeV. This astrophysical bound severely limits the possibilities for physics beyond the standard model below the scale of quantum gravity.

This new empirical prediction seems to be in direct conflict with their previous post-Higgs, pre-upgraded-LHC theoretical prediction of imminent TeV scale physics. Fortunately, the cosmic QCD ‘gravitational’ axion is exempt from this. That prediction was archived here for posterity.

Cosmological bounds on TeV-scale physics and beyond, Niayesh Afshordi and Elliot Nelson, Phys. Rev. D 93, 083505 (7 April 2016), DOI:10.1103/PhysRevD.93.083505

We study the influence of the fluctuations of a Lorentz invariant and conserved vacuum on cosmological metric perturbations, and show that they generically blow up in the IR. We compute this effect using the Källén-Lehmann spectral representation of stress correlators in generic quantum field theories, as well as the holographic bound on their entanglement entropy, both leading to an IR cut-off that scales as the fifth power of the highest UV scale (in Planck units). One may view this as analogous to the Heisenberg uncertainty principle, which is imposed on the phase space of gravitational theories by the Einstein constraint equations. The leading effect on cosmological observables come from anisotropic vacuum stresses which imply: i) any extension of the standard model of particle physics can only have masses (or resonances) ≲ 24 TeV, and ii) perturbative quantum field theory or quantum gravity becomes strongly coupled beyond a cut-off scale of Λ ≲ 1 PeV. Such a low cut-off is independently motivated by the Higgs hierarchy problem. This result, which we dub the cosmological non-constant problem, can be viewed as an extension of the cosmological constant (CC) problem, demonstrating the non-trivial UV-IR coupling and (yet another) limitation of effective field theory in gravity. However, it is more severe than the old CC problem, as vacuum fluctuations cannot be tuned to cancel due to the positivity of spectral densities or entropy. We thus predict that future advances in cosmological observations and collider technology will sandwich from above and below, and eventually discover, new (non-perturbative) physics beyond the Standard Model within the TeV-PeV energy range.

This was in the 750 GeV bump era, so it appears the sandwich has closed.

The empirical prediction seems more persuasive.

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Highly Speculative Quantum Gravity Hypothesis Explored

by Tommy on 8/04/2017

Sorry, I couldn’t help myself but this is so much fun.

A new length scale for quantum gravity, Tejinder P. Singh (3 April 2017)

We show why and how Compton wavelength and Schwarzschild radius should be combined into one single new length scale, which we call the Compton-Schwarzschild length. Doing so offers a resolution of the black hole information loss paradox, and suggests Planck mass remnant black holes as candidates for dark matter. It also compels us to introduce torsion, and identify the Dirac field with a complex torsion field. Dirac equation, and Einstein equations, are shown to be mutually dual limiting cases of an underlying gravitation theory which involves the Compton-Schwarzschild length scale, and includes a complex torsion field.

This was really difficult to wade through but following the references I like it.

I’m not too keen on primordial black holes though.

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Long Term Geochemical Carbon Cycle and Radiative Forcing

by Tommy on 5/04/2017

This is certainly worth reading, just for the weathering stuff.

Future climate forcing potentially without precedent in the last 420 million years, Gavin L. Foster, Dana L. Royer and Daniel J. Lunt, Nature Communications 8, 14845 (4 April 2017), doi:10.1038/ncomms14845

The evolution of Earth’s climate on geological timescales is largely driven by variations in the magnitude of total solar irradiance (TSI) and changes in the greenhouse gas content of the atmosphere. Here we show that the slow ∼ 50 Wm−2 increase in TSI over the last ∼ 420 million years (an increase of ∼9 Wm−2 of radiative forcing) was almost completely negated by a long-term decline in atmospheric CO2. This was likely due to the silicate weathering-negative feedback and the expansion of land plants that together ensured Earth’s long-term habitability. Humanity’s fossil-fuel use, if unabated, risks taking us, by the middle of the twenty-first century, to values of CO2 not seen since the early Eocene (50 million years ago). If CO2 continues to rise further into the twenty-third century, then the associated large increase in radiative forcing, and how the Earth system would respond, would likely be without geological precedent in the last half a billion years.

It’s official. Again. We’re screwed.

Happy 420 Day! Last Call.

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Chiral Axial Gravitational Anomaly Found in a Weyl Semimetal

by Tommy on 3/04/2017

And here it is!

Experimental signatures of the mixed axial-gravitational anomaly in the Weyl semimetal NbP, Johannes Gooth, Anna Corinna Niemann, Tobias Meng, Adolfo G. Grushin, Karl Landsteiner, Bernd Gotsmann, Fabian Menges, Marcus Schmidt, Chandra Shekhar, Vicky Sueß, Ruben Huehne, Bernd Rellinghaus, Claudia Felser, Binghai Yan and Kornelius Nielsch (29 March 2017)

Weyl semimetals are materials where electrons behave effectively as a kind of massless relativistic particles known as Weyl fermions. These particles occur in two flavours, or chiralities, and are subject to quantum anomalies, the breaking of a conservation law by quantum fluctuations. For instance, the number of Weyl fermions of each chirality is not independently conserved in parallel electric and magnetic field, a phenomenon known as the chiral anomaly. In addition, an underlying curved spacetime provides a distinct contribution to a chiral imbalance, an effect known as the mixed axial-gravitational anomaly, which remains experimentally elusive. However, the presence of a mixed gauge-gravitational anomaly has recently been tied to thermoelectrical transport in a magnetic field, even in flat spacetime, opening the door to experimentally probe such type of anomalies in Weyl semimetals. Using a temperature gradient, we experimentally observe a positive longitudinal magnetothermoelectric conductance (PMTC) in the Weyl semimetal NbP for collinear temperature gradients and magnetic fields (DT || B) that vanishes in the ultra quantum limit. This observation is consistent with the presence of a mixed axial-gravitational anomaly. Our work provides clear experimental evidence for the existence of a mixed axial-gravitational anomaly of Weyl fermions, an outstanding theoretical concept that has so far eluded experimental detection.

Some vindication is always nice.

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Cosmic Web Void Structure Evolution Mimics Dark Energy

by Tommy on 1/04/2017

I finally got around to getting up to date on the dark energy controversy.

Concordance cosmology without dark energy, Gábor Rácz, László Dobos, Róbert Beck, István Szapudi and István Csabai, Monthly Notices of the Royal Astromical Society Letters slx026 (12 February 2017), DOI:10.1093/mnrasl/slx026

According to the separate universe conjecture, spherically symmetric sub-regions in an isotropic universe behave like mini-universes with their own cosmological parameters. This is an excellent approximation in both Newtonian and general relativistic theories. We estimate local expansion rates for a large number of such regions, and use a scale parameter calculated from the volume-averaged increments of local scale parameters at each time step in an otherwise standard cosmological N-body simulation. The particle mass, corresponding to a coarse graining scale, is an adjustable parameter. This mean field approximation neglects tidal forces and boundary effects, but it is the first step towards a non-perturbative statistical estimation of the effect of non-linear evolution of structure on the expansion rate. Using our algorithm, a simulation with an initial Ωm = 1 Einstein-de~Sitter setting closely tracks the expansion and structure growth history of the ΛCDM cosmology. Due to small but characteristic differences, our model can be distinguished from the ΛCDM model by future precision observations. Moreover, our model can resolve the emerging tension between local Hubble constant measurements and the Planck best-fitting cosmology. Further improvements to the simulation are necessary to investigate light propagation and confirm full consistency with cosmic microwave background observations.

This has been out there for a while, but better late than never!

Update: ESA Euclid Consortium Mission

Euclid Consortium – A Space Mission to Map the Dark Universe

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The QCD Axion Stabilizes the Higgs Electroweak Vacuum

by Tommy on 31/03/2017

This exposition has been extremely helpful.

The QCD Axion and Electroweak Vacuum Stability, J. McDonald (14 March 2017)

The complex field Φ containing the QCD axion has a natural portal coupling to the Higgs doublet of the form λ |Φ|2 |H|2. Here we consider the possibility that λ has a natural magnitude for a dimensionless coupling, λ ∼ 0.1 − 1. This is possible if the total mass squared parameter of the Higgs in the vacuum, including quadratic divergent and the Φ vacuum expectation value contributions, is renormalized to reproduce the observed Higgs boson mass. It is then possible for the axion sector to stabilize the electroweak vacuum. We show the requirement of electroweak vacuum stability implies that the axion decay constant satisfies fa < 1.3 × 1010 GeV.

I want more of this.

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Calcium Ruthenate Ca2RuO4 Comes of Age

by Tommy on 30/03/2017

I have questions. I want answers.

Observation of localized high-Tc superconductivity in a Ca2RuO4 nanofilm single crystal, Hiroyoshi Nobukane, Kosei Yanagihara, Yuji Kunisada, Yunito Ogasawara, Kazushige Nomura, Yasuhiro Asano and Satoshi Tanda (28 March 2017)

We report two-dimensional superconducting phase fluctuations in a Ca2RuO4 nanofilm single crystal. A thin film of Ca2RuO4 exhibits typical Kosterlitz-Thouless transition behaviour around TKT = 30 K. We also found that the bias current applied to the thin film causes a superconducotor-insulator transition at low temperatures. The film is superconductive for small bias currents and insulating for large bias currents. The two phases are well separated by the critical sheet resistance of the thin film 16.5 kΩ. In addition to these findings, our results suggest the presence of superconducting fluctuations at a high temperature T = 96 K with onset. The fabrication of nanofilms made of layered material enables us to discuss rich superconducting phenomena in ruthenates.

Sr2RuO4 is already super interesting.

And contentious! That’s always fun.

See also: a penetrating neutron spectroscopy study of this system.

Magnon dispersion in Ca2RuO4: impact of spin-orbit coupling and oxygen moments, S. Kunkemöller, E. Komleva, S. V. Streltsov, S. Hoffmann, D. I. Khomskii, P. Steffens, Y. Sidis, K. Schmalzl and M. Braden (29 March 2017)

The magnon dispersion of Ca2RuO4 has been studied by polarized and unpolarized neutron scattering experiments on crystals containing 0, 1 and 10 % of Ti. The entire dispersion of transverse magnons can be well described by a conventional spin-wave model with interaction and anisotropy parameters that agree with density functional theory calculations. Spin-orbit coupling strongly influences the magnetic excitations, which is most visible in large energies of the magnetic zone-center modes arising from magnetic anisotropy. We find evidence for a low-lying additional mode that exhibits strongest scattering intensity near the antiferromagnetic zone center. This extra signal can be explained by a sizable magnetic moment of 0.11 Bohr magnetons on the apical oxygens parallel to the Ru moment, which is found in the density functional theory calculations. The energy and the signal strength of the additional branch are well described by taking into account this oxygen moment with weak ferromagnetic coupling between Ru and O moments.

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Possible Alkali Doped Organic Polymer Chain Superconductivity

by Tommy on 22/03/2017

I don’t know what to make of this, but potassium sounds about right for this kind of thing.

Superconductivity above 120 kelvin in a chain link molecule, Ren-Shu Wang, Yun Gao, Zhong-Bing Huang and Xiao-Jia Chen (20 March 2017)

The search for new superconducting compounds with higher critical temperatures Tcs has long been the very heart of scientific research on superconductivity. It took 75 years for scientists to push the Tc above liquid nitrogen boiling temperature since the discovery of superconductivity. So far, the record high Tc of about 130 K at atmosphere pressure was reported in some multilayer Hg(Tl)-Ba-Ca-Cu-O compounds. Meanwhile, sulfur hydride system holds the highest Tc of around 200 K at high pressure of about 150 GPa. While keeping these records for superconductivity, either the toxicity of these superconductors or the requirement of extreme pressure condition for superconductivity limits their technology applications. Here we show that doping a chain link molecule − p-terphenyl by potassium can bring about superconductivity at 123 K at atmosphere pressure, which is comparable to the highest Tc in cuprates. The easy processability, light weight, durability of plastics, and environmental friendliness of this kind of new superconductor have great potential for the fine-tuning of electrical properties. This study opens a window for exploring high temperature superconductivity in chain link organic molecules.

See also:

Superconductivity at 43 K in a single C-C bond linked terphenyl, Ren-Shu Wang, Yun Gao, Zhong-Bing Huang and Xiao-Jia Chen (16 March 2017)

Organic compounds are promising candidates to exhibit high temperature or room temperature superconductivity. However, the critical temperatures of organic superconductors are bounded to 38 K. By doping potassium into p-terphenyl consisting of C and H elements with three phenyl rings connected by single C-C bond in para position, we find that this material can have a superconducting phase with the critical temperature of 43 K. The superconducting parameters such as the critical fields, coherent length, and penetration depth are obtained for this superconductor. These findings open an encouraging window for the search of high temperature superconductors in chain link organic molecules.

From now on I’m only covering the Arxiv on Tuesdays. I was a bipolaron man way back.

I haven’t dabbled too much into it lately. Some of the more extreme bipolaron theories are occasionally considered crackpot, or at least historically so. Here, density counts.

I will have to take it at face value.

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Remarkable Two Dimensional Amorphized Graphene Produced

by Tommy on 21/03/2017

First there is amorphized bismuth iodide, now it’s amorphized graphene sheets.

The world of condensed matter physics is about to get a lot more exciting. Real soon now!

Amorphized graphene: A stiff material with low thermal conductivity, B Mortazavi, Z Fan, LFC Pereira, A Harju and T Rabczuk (17 March 2017), doi:10.1016/j.carbon.2016.03.007

All-carbon heterostructures have been produced recently via focused ion beam patterning of single layer graphene. Amorphized graphene is similar to a graphene sheet in which some hexagons are replaced by a combination of pentagonal, heptagonal and octagonal rings. The present investigation provides a general view regarding phonon and load transfer along amorphous graphene. The developed models for the evaluation of mechanical and thermal conductivity properties yield accurate results for pristine graphene and acquired findings for amorphized graphene films are size independent. Our atomistic results show that amorphous graphene sheets could exhibit a remarkably high elastic modulus of ~ 500 GPa and tensile strengths of ~ 50 GPa at room temperature. However, our results show that mechanical properties of amorphous graphene decline at higher temperatures. Furthermore, we show that amorphized graphene present a low thermal conductivity ~ 15 W/mK which is two orders of magnitude smaller than pristine graphene, and we verify that its thermal conductivity is almost insensitive to temperature since it is dominated by phonon-defect scattering rather than phonon-phonon scattering. Finally, our results show that amorphized graphene structures present a remarkably high elastic modulus and mechanical strength, along with a low thermal conductivity, which is an unusual combination for carbon-based materials.

I guess this has been out for a while, but it’s the first I heard of it!

I’ve only recently become interested in amorphization.

They just bumped it up to the Arxiv.

A sure way to boost readership.

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Spectral Weight Distributions in Superconducting Condensates

by Tommy on 21/03/2017

This is something I’ve known for a long time, but now it’s official.

Coexistence of non-Fermi liquid and Fermi liquid self-energies at all dopings in cuprates, Sujay Ray and Tanmoy Das (18 March 2017)

Non-Fermi liquid (NFL) state represents an ensemble of incoherent quantum fluids arising from the coupling between electrons and massless (critical) excitations, and is separated by phase boundary from the quasiparticle behavior in the Fermi-liquid (FL) theory. Here we show that such sharp distinction breaks down in cuprates, and that both NFL and FL states coexists in different momentum (k) regions at all dopings. Their coexistence originates from the strong anisotropy in the many-body self-energy, arising from dispersive density-density fluctuations. The self-energy attains maxima (NFL-like) in the region where density degeneracy is optimum (antinodal region), while the nodal region remains FL-like at all dopings. We attribute the global NFL/FL behavior via the calculation of the resistivity-temperature exponent (n). Surprisingly, we find that the entire Brillouin zone becomes neither fully incoherent, NFL-like even at optimal doping with n = 1, nor fully FL-like even at overdoping (n = 2). As density degeneracy increases in different materials with increasing superconducting Tc, n decreases; providing a microscopic explanation to this intriguing relationship. All results, including coexistence of NFL- and FL-self-energies in the k-space, and their doping, materials dependencies are compared with available experimental data, followed by definite predictions for future studies.

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Early Galaxy Formation Contrary to Conventional Dark Matter

by Tommy on 15/03/2017

Just when I start thinking deeply and critically about Sabine Hossenfelder’s idea of an inverse baryon anti-correlation of a mass variable gravitational dark matter vector axion boson, deeply tied to universal entropy production and thermodynamic energy balance, there is this result.

Strongly baryon-dominated disk galaxies at the peak of galaxy formation ten billion years ago, R. Genzel, N. M. Förster Schreiber, H. Übler, P. Lang, T. Naab, R. Bender, L. J. Tacconi, E. Wisnioski, S. Wuyts, T. Alexander, A. Beifiori, S. Belli, G. Brammer, A. Burkert, C. M. Carollo, J. Chan, R. Davies, M. Fossati, A. Galametz, S. Genel, O. Gerhard, D. Lutz, J. T. Mendel, I. Momcheva, E. J. Nelson, A. Renzini, R. Saglia, A. Sternberg, S. Tacchella, K. Tadaki and D. Wilman, Nature 543, 397–401 (16 March 2017), doi:10.1038/nature21685

In the cold dark matter cosmology, the baryonic components of galaxies — stars and gas — are thought to be mixed with and embedded in non-baryonic and non-relativistic dark matter, which dominates the total mass of the galaxy and its dark-matter halo. In the local (low-redshift) Universe, the mass of dark matter within a galactic disk increases with disk radius, becoming appreciable and then dominant in the outer, baryonic regions of the disks of star-forming galaxies. This results in rotation velocities of the visible matter within the disk that are constant or increasing with disk radius — a hallmark of the dark-matter model. Comparisons between the dynamical mass, inferred from these velocities in rotational equilibrium, and the sum of the stellar and cold-gas mass at the peak epoch of galaxy formation ten billion years ago, inferred from ancillary data, suggest high baryon fractions in the inner, star-forming regions of the disks. Although this implied baryon fraction may be larger than in the local Universe, the systematic uncertainties (owing to the chosen stellar initial-mass function and the calibration of gas masses) render such comparisons inconclusive in terms of the mass of dark matter. Here we report rotation curves (showing rotation velocity as a function of disk radius) for the outer disks of six massive star-forming galaxies, and find that the rotation velocities are not constant, but decrease with radius. We propose that this trend arises because of a combination of two main factors: first, a large fraction of the massive high-redshift galaxy population was strongly baryon-dominated, with dark matter playing a smaller part than in the local Universe; and second, the large velocity dispersion in high-redshift disks introduces a substantial pressure term that leads to a decrease in rotation velocity with increasing radius. The effect of both factors appears to increase with redshift. Qualitatively, the observations suggest that baryons in the early (high-redshift) Universe efficiently condensed at the centres of dark-matter haloes when gas fractions were high and dark matter was less concentrated.

See also:

The evolution of the Tully-Fisher relation between z ∼ 2.3 and z ∼ 0.9 with KMOS3D, H. Übler, N.M. Förster Schreiber, R. Genzel, E. Wisnioski, S. Wuyts, P. Lang, T. Naab, D.J. Wilman, M. Fossati, J.T. Mendel, A. Beifiori, S. Belli, R. Bender, G. Brammer, A. Burkert, J. Chan, R. Davies, M. Fabricius, A. Galametz, D. Lutz, I. Momcheva, E.J. Nelson, R.P. Saglia, S. Seitz, L.J. Tacconi, K. Tadaki and P.G. van Dokkum, Submitted to ApJ (13 March 2017)

We investigate the stellar mass and baryonic mass Tully-Fisher relations (TFRs) of massive star-forming disk galaxies at redshift z ∼ 2.3 and z ∼ 0.9 as part of the KMOS3D integral field spectroscopy survey. Our spatially resolved data allow reliable modelling of individual galaxies, including the effect of pressure support on the inferred gravitational potential. At fixed circular velocity, we find higher baryonic masses and similar stellar masses at z ∼ 2.3 as compared to z ∼ 0.9. Together with the decreasing gas-to-stellar mass ratios with decreasing redshift, this implies that the contribution of dark matter to the dynamical mass at the galaxy scale increases towards lower redshift. A comparison to local relations reveals a negative evolution of the stellar and baryonic TFR zero-points from z = 0 to z ∼ 0.9, no evolution of the stellar TFR zero-point from z ∼ 0.9 to z ∼ 2.3, but a positive evolution of the baryonic TFR zero-point from z ∼ 0.9 to z ∼ 2.3. We discuss a toy model of disk galaxy evolution to explain the observed, non-monotonic TFR evolution, taking into account the empirically motivated redshift dependencies of galactic gas fractions, and of the relative amount of baryons to dark matter on the galaxy and halo scales.

See also also:

Falling outer rotation curves of star-forming galaxies at 0.6 < z < 2.6 probed with KMOS3D and SINS/ZC-SINF, P. Lang, N.M. Förster Schreiber, R. Genzel, S. Wuyts, E. Wisnioski, A. Beifiori, S. Belli, R. Bender, G. Brammer, A. Burkert, J. Chan, R. Davies, M. Fossati, A. Galametz, S.K. Kulkarni, D. Lutz, J.T. Mendel, I.G. Momcheva, T. Naab, E.J. Nelson, R.P. Saglia, S. Seitz, S. Tacchella, L.J. Tacconi, K. Tadaki, H. Übler, P.G. van Dokkum and D.J. Wilman, Submitted to the Astrophysical Journal (16 March 2017)

We exploit the deep resolved Halpha kinematic data from the KMOS3D and SINS/zC-SINF surveys to examine the largely unexplored outer disk kinematics of star-forming galaxies (SFGs) out to the peak of cosmic star formation. Our sample contains 101 SFGs representative of the more massive (9.3 < log(M*/Msun) < 11.5) main sequence population at 0.6 < z < 2.6. Through a novel stacking approach we are able to constrain a representative rotation curve extending out to ~ 4 effective radii. This average rotation curve exhibits a significant drop in rotation velocity beyond the turnover, with a slope of Delta(V)/Delta(R) = −0.26+0.10−0.09 in units of normalized coordinates V/Vmax and R/Rturn. This result confirms that the fall-off seen previously in some individual galaxies is a common feature of our sample of high-z disks. We show that this outer fall-off strikingly deviates from the flat or mildly rising rotation curves of local spiral galaxies of similar masses. We furthermore compare our data with models including baryons and dark matter demonstrating that the falling stacked rotation curve can be explained by a high mass fraction of baryons relative to the total dark matter halo (md > ~ 0.05) in combination with a sizeable level of pressure support in the outer disk. These findings are in agreement with recent studies demonstrating that star-forming disks at high redshift are strongly baryon dominated within the disk scale, and furthermore suggest that pressure gradients caused by large turbulent gas motions are present even in their outer disks. We demonstrate that these results are largely independent of our model assumptions such as the presence of a central stellar bulge, the effect of adiabatic contraction at fixed md, and variations in the concentration parameter.

My gravitational axions are looking better all the time.

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Pressure Induced Topological Superconductivity of BiTeI Probed

by Tommy on 15/03/2017

Now that both Bi4I4 and BiTeI have been demonstrated to be unusual pressure induced topological superconductors, it would make sense to probe both of them more deeply with modern spectroscopic and ab initio analytical techniques. And it turns out that objective has already been performed on BiTeI.

Superconductivity Bordering Rashba Type Topological Transition, M. L. Jin, F. Sun, L. Y. Xing, S. J. Zhang, S. M. Feng, P. P. Kong, W. M. Li, X. C. Wang, J. L. Zhu, Y. W. Long, H. Y. Bai, C. Z. Gu, R. C. Yu, W. G. Yang, G. Y. Shen, Y. S. Zhao, H. K. Mao and C. Q. Jin, Scientific Reports 7, 39699 (4 January 2017), doi:10.1038/srep39699

Strong spin orbital interaction (SOI) can induce unique quantum phenomena such as topological insulators, the Rashba effect, or p-wave superconductivity. Combining these three quantum phenomena into a single compound has important scientific implications. Here we report experimental observations of consecutive quantum phase transitions from a Rashba type topological trivial phase to topological insulator state then further proceeding to superconductivity in a SOI compound BiTeI tuned via pressures. The electrical resistivity measurement with V shape change signals the transition from a Rashba type topological trivial to a topological insulator phase at 2 GPa, which is caused by an energy gap close then reopen with band inverse. Superconducting transition appears at 8 GPa with a critical temperature TC of 5.3 K. Structure refinements indicate that the consecutive phase transitions are correlated to the changes in the Bi–Te bond and bond angle as function of pressures. The Hall Effect measurements reveal an intimate relationship between superconductivity and the unusual change in carrier density that points to possible unconventional superconductivity.

Next up, Bi4I4.

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Record Breaking Weyl Semimetal Tungsten Diphosphide – WP2

by Tommy on 14/03/2017

It’s something new every day, for the guy who utterly failed to predict the iron arsenides in 1994.

Extremely high magnetoresistance and conductivity in the type-II Weyl semimetal WP2, Nitesh Kumar, Yan Sun, Kaustuv Manna, Vicky Suess, Inge Leermakers, Olga Young, Tobias Foerster, Marcus Schmidt, Binghai Yan, Uli Zeitler, Claudia Felser and Chandra Shekhar (13 March 2017)

The experimental realization of tungsten diphosphide, WP2, a type-II Weyl semimetal with robust Weyl points is presented. Weyl points are closely located to each other in the Brillouin zone but here are of the same chirality and are therefore protected against annihilation from structural distortions or defects. The single crystals show extremely high residual resistivity (RRR) values of 25,000 with a very low residual resistivity of 3 nano-ohm cm, and an enormous, highly anisotropic, magnetoresistance that exceeds 200 million percent at 63 T and 0.5 K. These properties are likely a consequence of the novel fermions expressed in this compound.

I did point out that any metal-insulator sitting across the metalloid band would be cool, though.

In this case, very cool.

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I’m an American. I Love America, Don’t Let Me Down.

by Tommy on 12/03/2017

March 20, 2017, on CSPAN.

Be there or be square.

Update: Happy Pi Day!

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Sabine Hossenfelder Discovers a Vector Axion Condensate

by Tommy on 12/03/2017

Sort of. I haven’t really had time to work through the math yet.

But this is promising that axions may indeed be gravitational.

Or alternatively that gravitational spacetime may be emergent.

I sense a duality in progress. That means a song may be coming on!

Is Verlinde’s Emergent Gravity compatible with General Relativity?

A Covariant Version of Verlinde’s Emergent Gravity, Sabine Hossenfelder (4 March 2017)

A generally covariant version of Erik Verlinde’s emergent gravity model is proposed. The Lagrangian constructed here allows an improved interpretation of the underlying mechanism. It suggests that de-Sitter space is filled with a vector-field that couples to baryonic matter and, by dragging on it, creates an effect similar to dark matter. We solve the covariant equation of motion in the background of a Schwarzschild space-time and obtain correction terms to the non-covariant expression. Furthermore, we demonstrate that the vector field can also mimic dark energy.

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Higgs Amplitude Modes, Goldstone Modes, Pair Density Waves

by Tommy on 9/03/2017

And of course Eduardo Fradkin et al., at the University of Illinois Urbana-Champaign rocks.

Check out this study. They’re doing quantum cosmology and they don’t even know it!

Higgs Modes in the Pair Density Wave Superconducting State, Rodrigo Soto-Garrido, Yuxuan Wang, Eduardo Fradkin and S. Lance Cooper (7 March 2017)

The pair density wave (PDW) superconducting state has been proposed to explain the layer- decoupling effect observed in the compound La2−xBaxCuO4 at x = 1/8 (Phys. Rev. Lett. 99, 127003). In this state the superconducting order parameter is spatially modulated, in contrast with the usual superconducting (SC) state where the order parameter is uniform. In this work, we study the properties of the amplitude (Higgs) modes in a unidirectional PDW state. To this end we consider a phenomenological model of PDW type states coupled to a Fermi surface of fermionic quasiparticles. In contrast to conventional superconductors that have a single Higgs mode, unidirectional PDW superconductors have two Higgs modes. While in the PDW state the Fermi surface largely remains gapless, we find that the damping of the PDW Higgs modes into fermionic quasiparticles requires exceeding an energy threshold. We show that this suppression of damping in the PDW state is due to kinematics. As a result, only one of the two Higgs modes is significantly damped. In addition, motivated by the experimental phase diagram, we discuss the mixing of Higgs modes in the coexistence regime of the PDW and uniform SC states. These results should be observable directly in a Raman spectroscopy, in momentum resolved electron energy loss spectroscopy, and in resonant inelastic X-ray scattering, thus providing evidence of the PDW states.

You need to read this paper because this is as good as it gets nowadays.

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Penetrating But Not Yet Definitive Probe of Strontium Ruthenate

by Tommy on 9/03/2017
Strontium Ruthenate Under Strain

Strontium Ruthenate Under Strain

If you have been paying attention, strontium ruthenate, Sr2RuO4, is still controversial.

It’s as controversial as the cuprates were back in 1994 when it was first discovered to be superconducting. Here it is demonstrated that there is a one dimensional sub-character reminiscent of bismuth iodide, Bi4I4. And unixial stress, which has not yet been applied to bismuth iodide, elevated the critical transition temperature. Bismuth iodide is up next for this.

Quasiparticle Interference and Strong Electron-Mode Coupling in the Quasi-One-Dimensional Bands of Sr2RuO4, Zhenyu Wang, Daniel Walkup, Philip Derry, Thomas Scaffidi, Melinda Rak, Sean Vig, Anshul Kogar, Ilija Zeljkovic, Ali Husain, Luiz H. Santos, Yuxuan Wang, Andrea Damascelli, Yoshiteru Maeno, Peter Abbamonte, Eduardo Fradkin and Vidya Madhavan
(10 January 2017)

The single-layered ruthenate Sr2RuO4 has attracted a great deal of interest as a spin-triplet superconductor with an order parameter that may potentially break time reversal invariance and host half-quantized vortices with Majorana zero modes. While the actual nature of the superconducting state is still a matter of controversy, it has long been believed that it condenses from a metallic state that is well described by a conventional Fermi liquid. In this work we use a combination of Fourier transform scanning tunneling spectroscopy (FT-STS) and momentum resolved electron energy loss spectroscopy (M-EELS) to probe interaction effects in the normal state of Sr2RuO4. Our high-resolution FT-STS data show signatures of the \beta-band with a distinctly quasi-one-dimensional (1D) character. The band dispersion reveals surprisingly strong interaction effects that dramatically renormalize the Fermi velocity, suggesting that the normal state of Sr2RuO4 is that of a ‘correlated metal’ where correlations are strengthened by the quasi 1D nature of the bands. In addition, kinks at energies of approximately 10 meV, 38 meV and 70 meV are observed. By comparing STM and M-EELS data we show that the two higher energy features arise from coupling with collective modes. The strong correlation effects and the kinks in the quasi 1D bands may provide important information for understanding the superconducting state. This work opens up a unique approach to revealing the superconducting order parameter in this compound.

See also:

Strong peak in Tc of Sr2RuO4 under uniaxial pressure, Alexander Steppke, Lishan Zhao, Mark E. Barber, Thomas Scaffidi, Fabian Jerzembeck, Helge Rosner, Alexandra S. Gibbs, Yoshiteru Maeno, Steven H. Simon and Andrew P. Mackenzie, Clifford W. Hicks, Science, 355, eaaf9398 (13 January 2017), doi:0.1126/science.aaf9398

We report a combined experimental and theoretical study of the dependence of the superconductivity of the unconventional superconductor Sr2RuO4 on anisotropic strain. Novel piezoelectric apparatus is used to apply uniaxial pressures of up to ∼1 GPa along a ⟨100⟩ direction (a-axis) of the crystal lattice. Tc increases from 1.5 K in unstrained material to 3.4 K at compression by ≈ 0.6%, then falls steeply. The c-axis upper critical field for the strained Tc = 3.4 K material is a factor of twenty larger than that of the unstrained crystal, whereas the in-plane (a-axis) critical field increases by only a factor of three. First-principles electronic structure calculations give evidence that the observed maximum Tc occurs at or near a Lifshitz transition when the Fermi level passes through a van Hove singularity. Finally, we perform order parameter analyses using three-band renormalization group calculations. These, combined with the unexpectedly low in-plane critical field, open the possibility that the highly strained Tc = 3.4 K Sr2RuO4 has an even- rather than an odd-parity order parameter. Potential implications such as a transition at nonzero strain between odd- and even-parity order parameters are discussed.

Now this is getting really interesting. And don’t forget … axions!

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Particulate Cold Dark Matter Found By Galactic Cluster Lensing

by Tommy on 1/03/2017
Dark Matter Galactic Cluster Lensing

Dark Matter Galactic Cluster Lensing

I don’t think the modified gravity people will accept defeat, but here it is.

Mapping substructure in the HST Frontier Fields cluster lenses and in cosmological simulations, Priyamvada Natarajan, Urmila Chadayammuri, Mathilde Jauzac, Johan Richard, Jean-Paul Kneib, Harald Ebeling, Fangzhou Jiang, Frank van den Bosch, Marceau Limousin, Eric Jullo, Hakim Atek, Annalisa Pillepich, Cristina Popa, Federico Marinacci, Lars Hernquist, Massimo Meneghetti and Mark Vogelsberger, Mon Not R Astron Soc, stw3385 (6 February 2017), doi:10.1093/mnras/stw3385

We map the lensing-inferred substructure in the first three clusters observed by the Hubble Space Telescope Frontier Fields Initiative (HSTFF): Abell 2744 (z = 0.308), MACSJ 0416, (z = 0.396) and MACSJ 1149 (z = 0.543). Statistically resolving dark-matter subhaloes down to ∼109.5 M, we compare the derived subhalo mass functions (SHMFs) to theoretical predictions from analytical models and with numerical simulations in a Lambda Cold Dark Matter (LCDM) cosmology. Mimicking our observational cluster member selection criteria in the HSTFF, we report excellent agreement in both amplitude and shape of the SHMF over four decades in subhalo mass (109 − 13 M). Projection effects do not appear to introduce significant errors in the determination of SHMFs from simulations. We do not find evidence for a substructure crisis, analogous to the missing satellite problem in the Local Group, on cluster scales, but rather excellent agreement of the count-matched HSTFF SHMF down to Msubhalo/Mhalo ∼ 10−5. However, we do find discrepancies in the radial distribution of sub haloes inferred from HSTFF cluster lenses compared to determinations from simulated clusters. This suggests that although the selected simulated clusters match the HSTFF sample in mass, they do not adequately capture the dynamical properties and complex merging morphologies of these observed cluster lenses. Therefore, HSTFF clusters are likely observed in a transient evolutionary stage that is presently insufficiently sampled in cosmological simulations. The abundance and mass function of dark matter substructure in cluster lenses continues to offer an important test of the LCDM paradigm, and at present we find no tension between model predictions and observations.

Yale-led team puts dark matter on the map, By Jim Shelton

Yale University Press Release

Take that, Harvard!

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Collective Modes and Defects Implicated in Phase Transitions

by Tommy on 25/02/2017

Here is yet another brilliant study.

In situ study on atomic mechanism of melting and freezing of single bismuth nanoparticles, Yingxuan Li, Ling Zang, Daniel L. Jacobs, Jie Zhao, Xiu Yue and Chuanyi Wang, Nature Communications 8, 14462 (13 February 2017), doi:10.1038/ncomms14462

Experimental study of the atomic mechanism in melting and freezing processes remains a formidable challenge. We report herein on a unique material system that allows for in situ growth of bismuth nanoparticles from the precursor compound SrBi2Ta2O9 under an electron beam within a high-resolution transmission electron microscope (HRTEM). Simultaneously, the melting and freezing processes within the nanoparticles are triggered and imaged in real time by the HRTEM. The images show atomic-scale evidence for point defect induced melting, and a freezing mechanism mediated by crystallization of an intermediate ordered liquid. During the melting and freezing, the formation of nucleation precursors, nucleation and growth, and the relaxation of the system, are directly observed. Based on these observations, an interaction–relaxation model is developed towards understanding the microscopic mechanism of the phase transitions, highlighting the importance of cooperative multiscale processes.

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Frenkel Phonon Theory of Liquid Thermodynamics Developed

by Tommy on 24/02/2017

This qualifies as a landmark study.

Direct links between dynamical, thermodynamic and structural properties of liquids: modelling results, L. Wang, C. Yang, M. T. Dove, Yu. D. Fomin, V. V. Brazhkin and K. Trachenko (23 February 2017)

We develop an approach to liquid thermodynamics based on collective modes. We perform extensive molecular dynamics simulations of noble, molecular and metallic liquids and provide the direct evidence that liquid energy and specific heat are well-described by the temperature dependence of the Frenkel (hopping) frequency. The agreement between predicted and calculated thermodynamic properties is seen in the notably wide range of temperature spanning tens of thousands of Kelvin. The range includes both subcritical liquids and supercritical fluids. We discuss the structural crossover and inter-relationships between structure, dynamics and thermodynamics of liquids and supercritical fluids.

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Analytic and Numerical Ab Initio Analysis of Hydrogen Bilayers

by Tommy on 24/02/2017

This should help sort out the great hydrogen metallization war before it escalates further.

Metallization of solid molecular hydrogen in two dimensions: Mott-Hubbard-type transition, Andrzej Biborski, Andrzej P. Kądzielawa and Józef Spałek (21 February 2017)

We analyze the pressure-induced metal-insulator transition in a two-dimensional vertical stack of H2 molecules in x-y plane, and show that it represents a striking example of the Mott-Hubbard-type transition. Our combined exact diagonalization approach, formulated and solved in the second quantization formalism, includes also simultaneous ab initio readjustment of the single-particle wave functions, contained in the model microscopic parameters. The system is studied as a function of applied side force (generalized pressure), both in the H2-molecular and H-quasiatomic states. Extended Hubbard model is taken at the start, together with longer-range electron-electron interactions incorporated into the scheme. The stacked molecular plane transforms discontinuously into a (quasi)atomic state under the applied force via a two-step transition: the first between molecular insulating phases and the second from the molecular to the quasiatomic metallic phase. No quasiatomic insulating phase occurs. All the transitions are accompanied by an abrupt changes of the bond length and the intermolecular distance (lattice parameter), as well as by discontinuous changes of the principal electronic properties, which are characteristic of the Mott-Hubbard transition here associated with the jumps of the predetermined equilibrium lattice parameter and the effective bond length. The phase transition can be interpreted in terms of the solid hydrogen metallization under pressure exerted by e.g., the substrate covered with a monomolecular H2 film of the vertically stacked molecules. Both the Mott and Hubbard criteria at the insulator to metal transition are discussed.

This work is of extremely high quality.

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On the Nature of Bismuth (I) Iodide Bi+ Bi1+ Part 2 II Two

by Tommy on 19/02/2017

Just when I want to quit blobbing for the nth time, I am distracted yet again.

What does an anxious science blogger without a career and no clue and flat broke, do about it?

Answer: Continue to solve interesting outstanding major problems of the universe, and report.

And maybe a speculative rant or two thrown in for good measure. Since I do these things for my own personal enlightenment, who cares. Things rarely work out the way I plan anyways, which is why I keep Plan B and C and even D handy, just in case. Cases in point, the Younger Dryas Impact Hypothesis. How long do I cling to that? That’s as nutty as a comet impact initiating the Paleocene Eocene Thermal Maximum (PETM). So far in the literature we have ice blocks as ejecta from the Black Sturgeon River Basin arcing parabolically (is that a word?) all the way down the the Eastern seaboard and excavating numerous oval basins in the lowland muck.

A model for the Geomorphology of the Carolina Bays, Antonio Zamora, Geomorphology 282, 209–216 (1 April 2017)

So yeah, it’s time to move on with that.

What about reusable rocketry? Time to move on. To Mars, hopefully, or wherever there are good jobs and no religious fascists. Or Swedenborgia. That’s it. With a big check and a diploma and a handshake from the King and hopefully a permanent (or at least an eight year) position at the Institute. That could work! My girlfriend wants in already, and she’s Swedish, or at least partly Swedenborgian. And I assume Sweden will eventually want a space program too. Everyone does nowadays. Nova Scotia is looking good. If New Zealand can do it, Canada can do it too.

What has all of this have to do with bismuth iodide?

In a word – amorphization.

My new favorite word.

Update 1: So it is decided. I will have to write yet another crackpot essay.

So stay tuned. More nonsense from the peanut gallery yet to come.

Update 2: I guess it’s Planet E, then.

Update 3: It has begun.

I’ll try to get something together in the next few weeks.

High Pressure Amorphization of Bi4I4 – Bi+ Formation and Superconductivity

The recent demonstration of high pressure superconductivity in the exotic topological insulator Bi4I4, through a presumed amophization process, can be understood as the formation of an irregular lattice of monovalent bismuth ions – Bi+, and the predicted electronic Bose-Einstein condensation of bosons.

An obvious prediction derived from this scenario is a density dependent critical transition temperature.

I think I can do this. Let the great bismuth iodide war begin!

Update 4: While I’m at it there is also this.

Quantum Gravity Gauge Field Theory

The gravitational axion hypothesis previously proposed as cosmic QCD axions, or Peccei Quinn axions with additional low energy standard model couplings, is reduced to mathematics using a modern gauge field theory cast in the form of topological quantum field theory known from condensed matter physics.

In order to maintain contact with discernible reality the principle components of such a theory will be a spin-2 boson called a graviton, and a spin-0 boson called the axion, along with standard model physics.

So I am way in over my head in the sea of bosons.

I hate axions. They follow me everywhere.

The gravity on this planet is heavy.

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New Haloscope Searches For Dark Matter Axions Proposed

by Tommy on 18/02/2017

The race to detect the microwave dark matter axion is finally on.

Haloscope searches for dark matter axions at the Center for Axion and Precision Physics Research, Eleni Petrakou, Proceedings of the ICFNP 2016 Conference (13 February 2017)

The Center for Axion and Precision Physics Research (CAPP) was founded in 2013, with the ambition of shedding light on the strong CP problem and the proposed existence of axions. Much of CAPP’s effort focuses on the direct detection of dark matter candidate axions with a series of local haloscope experiments, which endeavour to expand dramatically the coverage on the “invisible axion” mass range. The first two of them plan experimental runs during this year, tapping into ultra-low cryogenics and toroidal cavity geometries. The overall programme builds on cutting-edge technology, including developments in superconducting films, SQUID amplifiers and novel magnets. This article presents the planned advancements and the status of the programme, while it can also be considered a pedagogical introduction to haloscope experiments.

Did I also mention that bismuth iodide is a topological superconductor?

You’ll be hearing that for a while too.

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The High Pressure Superconductivity of β-Bi4I4 Bismuth Iodide

by Tommy on 17/02/2017

So I will leave you with this last interesting tidbit.

It appears to me that my career possibilities have just increased remarkably.

Pressure effect and Superconductivity in β-Bi4I4 Topological Insulator Pressure effect and Superconductivity in β-Bi4I4 Topological Insulator, A. Pisoni, R. Gaal, A. Zeugner, V. Falkowski, A. Isaeva, H. Huppertz, G. Autes, O. V. Yazyev and L. Forro (15 February 2017)

We report a detailed study of the transport coefficients of β-Bi4I4 quasi-one dimensional topological insulator. Electrical resistivity, thermoelectric power, thermal conductivity and Hall coefficient measurements are consistent with the possible appearance of a charge density wave order at low temperatures. Both electrons and holes contribute to the conduction in β-Bi4I4 and the dominant type of charge carrier changes with temperature as a consequence of temperature-dependent carrier densities and mobilities. Measurements of resistivity and Seebeck coefficient under hydrostatic pressure up to 2 GPa show a shift of the charge density wave order to higher temperatures suggesting a strongly one-dimensional character at ambient pressure. Surprisingly, superconductivity is induced in β-Bi4I4 above 10 GPa with of 4.0 K which is slightly decreasing upon increasing the pressure up to 20 GPa. Chemical characterisation of the pressure-treated samples shows amorphization of β-Bi4I4 under pressure and rules out decomposition into Bi and BiI3 at room-temperature conditions.

See also:

Pressure-induced superconductivity and topological quantum phase transitions in a quasi-one-dimensional topological insulator: Bi4I4, Yanpeng Qi, Wujun Shi, Peter Werner, Pavel G. Naumov, Walter Schnelle, Lei Wang, Kumari Gaurav Rana, Stuart Parkin, Sergiy A. Medvedev, Binghai Yan and Claudia Felser (30 January 2017)

Superconductivity and topological quantum states are two frontier fields of research in modern condensed matter physics. The realization of superconductivity in topological materials is highly desired, however, superconductivity in such materials is typically limited to two- or three-dimensional materials and is far from being thoroughly investigated. In this work, we boost the electronic properties of the quasi-one-dimensional topological insulator bismuth iodide β-Bi4I4 by applying high pressure. Superconductivity is observed in β-Bi4I4 for pressures where the temperature dependence of the resistivity changes from a semiconducting-like behavior to that of a normal metal. The superconducting transition temperature Tc increases with applied pressure and reaches a maximum value of 6 K at 23 GPa, followed by a slow decrease. Our theoretical calculations suggest the presence of multiple pressure-induced topological quantum phase transitions as well as a structural-electronic instability.

So with all this treason crap I guess I have not been paying attention.

Didn’t I predict this? Well, maybe not, exactly.

Amorphization of a polymer?

Very suspicious.

On the Nature of Bismuth (I) Iodide in the Solid State

Thomas Lee Elifritz, Spec. Sci. Tech. 17, 85 (1994)

So this is almost, but not quite, a wrap.

It won’t be long now, trust me.

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Mathematical Description of Bulk Boundary Correspondances

by Tommy on 5/02/2017

This is some great stuff if you are into this kind of mathematics as I am.

Boundary-bulk relation in topological orders, Liang Kong, Xiao-Gang Wen, Hao Zheng (2 February 2017)

In this paper, we study the relation between an anomaly-free n+1D topological order, which are often called n+1D topological order in physics literature, and its nD gapped boundary phases. We argue that the n+1D bulk anomaly-free topological order for a given nD gapped boundary phase is unique. This uniqueness defines a notion of the “bulk” for a given gapped boundary phase. In this paper, we show that the n+1D “bulk” phase is given by the “center” of the nD boundary phase. In other words, the geometric notion of the “bulk” corresponds precisely to the algebraic notion of the “center”. We achieve this by first introducing the notion of a morphism between two (potentially anomalous) topological orders of the same dimension, then proving that the notion of “bulk” satisfying the same universal property as that of the “center” of an algebra in mathematics, i.e. “bulk = center”. The entire argument does not require us to know the precise mathematical description of a (potentially anomalous) topological order. This result leads to concrete physical predictions.

There are some very interesting physical ramifications here too.

Happy Groundhog’s Day! Again.

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The Origin of Life from Non-Equilibrium Thermodynamics

by Tommy on 1/02/2017

Ok, so now David Ruelle threw his hat into the origin of life world. That’s a good thing.

The origin of life seen from the point of view of non-equilibrium statistical mechanics, David Ruelle (29 January 2017)

This note presents a minimal approach to the origin of life, following standard ideas. We pay special attention to the point of view of non-equilibrium statistical mechanics, and in particular to detailed balance. As a consequence we propose a characterization of pre-biological states.

More is better, I say.

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Topological Θ Theta Physics and Chern Structure Confirmed in Strontium Ruthenate Sr2RuO4 Nanofilms

by Tommy on 29/01/2017

This is a long experimental treatise first reported by me here, beginning my axion adventure.

Topological Magneto Electric Effect by Chern Structure in Strontium Ruthenate – Sr2RuO4

You know me, I really don’t get interested in something unless it has contact with reality.

Chern structure in the Bose-insulating phase of Sr2RuO4 nanofilms, Hiroyoshi Nobukane, Toyoki Matsuyama and Satoshi Tanda, Scientific Reports 7, 41291 (23 January 2017), doi:10.1038/srep41291

The quantum anomaly that breaks the symmetry, for example the parity and the chirality, in the quantization leads to a physical quantity with a topological Chern invariant. We report the observation of a Chern structure in the Bose-insulating phase of Sr2RuO4 nanofilms by employing electric transport. We observed the superconductor-to-insulator transition by reducing the thickness of Sr2RuO4 single crystals. The appearance of a gap structure in the insulating phase implies local superconductivity. Fractional quantized conductance was observed without an external magnetic field. We found an anomalous induced voltage with temperature and thickness dependence, and the induced voltage exhibited switching behavior when we applied a magnetic field. We suggest that there was fractional magnetic-field-induced electric polarization in the interlayer. These anomalous results are related to topological invariance. The fractional axion angle Θ = π/6 was determined by observing the topological magneto-electric effect in the Bose-insulating phase of Sr2RuO4 nanofilms.

The p-wave nature of the superconductivity in Sr2RuO4 is still fairly controversial.

See also:

Emergence of the Chern structure using Sr2RuO4 nanofilms, Hiroyoshi Nobukane, Toyoki Matsuyama and Satoshi Tanda (6 August 2015)

We discovered a fractional Chern structure in chiral superconducting Sr2RuO4 nanofilms by employing electric transport. By using Sr2RuO4 single crystals with nanoscale thickness, a fractional Hall conductance was observed without an external magnetic field. The Sr2RuO4 nanofilms enhanced the superconducting transition temperature to about 3 K. We found an anomalous induced voltage with temperature and thickness dependence, and the switching behavior of the induced voltage appeared when we applied a magnetic field. We suggest that there was fractional magnetic-field-induced electric polarization in the interlayer. These anomalous results are related to topological invariance. The fractional axion angle θ=π/6 is determined by observing the topological magneto-electric effect in Sr2RuO4 nanofilms.

See also also:

Topological electromagnetic response in the chiral superconductor Sr2RuO4, Hiroyoshi Nobukane, Toyoki Matsuyama and Satoshi Tanda, Physica B: Condensed Matter, 460, 168–170 (1 March 2015), doi:10.1016/j.physb.2014.11.062

We report the observation of a fractional topological magneto-electric effect in Sr2RuO4 single crystal thin films by measuring the electric transport properties. In the absence of an external magnetic field, the surface transport in Sr2RuO4 thin films exhibited a fractional quantum Hall conductance in the superconducting state. The fractional magnetic-field-induced electric polarization was observed under zero bias current. We can understand the fractional quantum Hall conductance as a consequence of the observation of the (2+1) – dimensional topological surface state in the (3+1) – dimensional fractional topological magneto-electric effect in Sr2RuO4 thin films.

When I was first learning about axion physics, I considered this to be the big breakthrough.

The Scientific Reports article is open. Enjoy!

Is my axion adventure over now?

You tell me. I wanna know.

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Quantum Cosmology as Condensed Matter Physics Catches On

by Tommy on 28/01/2017

Frank Wikczek gets it. Finally. This idea is really catching on.

‘Nothing’ and the universe

Arizona State University’s Origins Project is hosting a lecture by Nobel Laureate Frank Wilczek, where he will discuss the “Materiality of a Vacuum: Late Night Thoughts of a Physicist” at 7 p.m. Tuesday, Jan. 31, at the Tempe Center for the Arts.

Tickets for “Materiality of a Vacuum: Late Night Thoughts of a Physicist” are $7 and $17. ASU students can obtain free tickets (two tickets per student ID to be picked up the venue box office) for the event. A book signing and pizza will follow the event.

The Tempe Center for the Arts box office is located at 700 W. Rio Salado Parkway, or call 480-350-2822.

For more information on Origins events, please go to or call (480) 965-0053.

I didn’t realize science was going to be this expensive though.

Books need to be sold because bills need to be paid.

In my case, they need to be written first.

Dark Matter Vixens From Venus.

Macho Wimps are outraged.

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Historical Development of ΛCDM and Dark Matter Discussed

by Tommy on 28/01/2017

This was an interesting read, particularly for a newbie like myself.

How the Nonbaryonic Dark Matter Theory Grew, P. J. E. Peebles, An essay to accompany articles on dark matter detection in Nature Astronomy (20 January 2017)

The evidence is that the mass of the universe is dominated by an exotic nonbaryonic form of matter largely draped around the galaxies. It approximates an initially low pressure gas of particles that interact only with gravity, but we know little more than that. Searches for detection thus must follow many difficult paths to a great discovery, what the universe is made of. The nonbaryonic picture grew out of a convergence of evidence and ideas in the early 1980s. Developments two decades later considerably improved the evidence, and advances since then have made the case for nonbaryonic dark matter compelling.

Let me show you how newbie is said properly.


You have your path.

I have mine.

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Isaac Silvera Manages to Finally Smush Hydrogen to a Metal

by Tommy on 27/01/2017

Here are some cool numbers for you.

Observation of the Wigner-Huntington transition to metallic hydrogen, Ranga P. Dias and Isaac F. Silvera, Science (26 January 2017), doi:10.1126/science.aal1579

Producing metallic hydrogen has been a great challenge to condensed matter physics. Metallic hydrogen may be a room temperature superconductor and metastable when the pressure is released and could have an important impact on energy and rocketry. We have studied solid molecular hydrogen under pressure at low temperatures. At a pressure of 495 GPa hydrogen becomes metallic with reflectivity as high as 0.91. We fit the reflectance using a Drude free electron model to determine the plasma frequency of 32.5 ± 2.1 eV at T = 5.5 K, with a corresponding electron carrier density of 7.7 ± 1.1 × 1023 particles/cm3, consistent with theoretical estimates of the atomic density. The properties are those of an atomic metal. We have produced the Wigner-Huntington dissociative transition to atomic metallic hydrogen in the laboratory.

Wow, that’s three times the charge carrier density of bismuth iodide.

Update 1: Nobody believes this, apparently. Who knew!

Update 2: Eremets et al. checks in.

Comments on the claimed observation of the Wigner-Huntington Transition to Metallic Hydrogen, M.I. Eremets and A. P. Drozdov (16 February 2017)

In their recent work Dias and Silvera (Science 2017) claim to have observed the Wigner-Huntington transition of hydrogen to a metallic state (MH) at a pressure of 495 GPa at low temperatures. The evidence for this transition is based on a high electron carrier density deduced from a Drude free electron model fitted to the reflectivity of the sample. Based on our analysis of the reflectivity data we find no convincing evidence for metallic hydrogen in their published data. The pressure determination is also ambiguous – it should be ~630 GPa according to the presented Raman spectrum. For comparison, we present our own data on the observation of highly reflecting hydrogen at pressures of 350-400 GPa. The appearance of metallic reflectivity is accompanied with a finite electrical conductivity of the sample. We argue that the actual pressure in the experiment of Dias and Silvera is likely below 400 GPa. In this case the observed enhanced reflectivity would be related to the phase transformation to conductive state published in arXiv:1601.04479.

So I can’t wait until they smush bismuth iodide again.

It won’t take this much effort.

I want a third opinion.

Update 3: Yet another published dissenting opinion.

Comment on: Observation of the Wigner-Huntington transition to metallic hydrogen, Paul Loubeyre, Florent Occelli and Paul Dumas (23 February 2017)

In a recently published article, Ranga P. Dias & Isaac F. Silvera have reported the visual evidence of metallic hydrogen concomitantly with its characterization at a pressure of 495 GPa and low temperatures. We have expressed serious doubts of such a conclusion when interviewed to comment on this publication. In the following comment, we would like to detail the reasons, based on experimental evidences obtained by us and by other groups worldwide that sustain our skepticism. We have identified two main flaws in this paper, as discussed in details below: the pressure is largely overestimated; the origin of the sample reflectivity and the analysis of the reflectance can be seriously questioned.

This will all be forgotten when they start smushing bismuth iodide, with extra hydrogen.

Update 4: Apparently the metallic hydrogen evaporated and escaped the vwessel. Vwessel.

If you have seen this vapor, please return it to its rightful owner. Thanks.

Update 5: And finally, this devastating comeback.

Comment on “Observation of the Wigner-Huntington transition to metallic hydrogen”, Xiao-Di Liu, Philip Dalladay-Simpson, Ross T. Howie, Bing Li and Eugene Gregoryanz (25 April 2017)

Dias and Silvera (Letters, p. 715, 2017) claim the observation of the Wigner-Huntington transition to metallic hydrogen at 495 GPa. We show that neither the claims of the record pressure or the phase transition to a metallic state are supported by any data and contradict the authors’ own unconfirmed previous results.

You know the saying, if at first you don’t succeed …

I’m sure they will get this all sorted out.

No Comments

The Microscopic Mechanism of Superconductivity in FeSe

by Tommy on 27/01/2017

Behold the spectroscopic microscopic mechanism theory era of superconductivity.

Mechanism for nematic superconductivity in FeSe, Jian-Huang She, Michael J. Lawler and Eun-Ah Kim (26 January 2017)

Despite its seemingly simple composition and structure, the pairing mechanism of FeSe remains an open problem due to several striking phenomena. Among them are nematic order without magnetic order, nodeless gap and unusual inelastic neutron spectra with a broad continuum, and gap anisotropy consistent with orbital selection of unknown origin. Here we propose a microscopic description of a nematic quantum paramagnet that reproduces key features of neutron spectra averaged over nematic domains. We then study how the spin fluctuations of the local moments lead to pairing within a spin-fermion model. We find the resulting superconducting order parameter to be nodeless s ± d-wave within each domain. Further we show that orbital selective Hund’s coupling can readily capture observed gap anisotropy. Our prediction for the inelastic neutron spectra within a single nematic domain calls for inelastic neutron scattering in a detwinned sample.

The microspectroscopic era.

See also:

FeTe1−xSex monolayer films: towards the realization of high-temperature connate topological superconductivity, Xun Shi, Zhiqing Han, Pierre Richard, Xianxin Wu, Xiliang Peng, Tian Qian, Shancai Wang, Jiangping Hu, Yujie Sun and Hong Ding (26 January 2017)

We performed angle-resolved photoemission spectroscopy studies on a series of FeTe1−xSex monolayer films grown on SrTiO3. The superconductivity of the films is robust and rather insensitive to the variations of the band position and effective mass caused by the substitution of Se by Te. However, the band gap between the electron- and hole-like bands at the Brillouin zone center decreases towards band inversion and parity exchange, which drive the system to a nontrivial topological state predicted by theoretical calculations. Our results provide a clear experimental indication that the FeTe1−xSex monolayer materials are high-temperature connate topological superconductors in which band topology and superconductivity are integrated intrinsically.

Now extend that microscopic theory into this.

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Electromagnetic Energy in Axion Haloscopes and Cavities

by Tommy on 23/01/2017

This showed up in the popular press this morning, finally.

Electric and magnetic energy at axion haloscopes, B. R. Ko, H. Themann, W. Jang, J. Choi, D. Kim, M. J. Lee, J. Lee, E. Won, and Y. K. Semertzidis, Phys. Rev. D 94, 111702(R) (9 December 2016), doi:10.1103/PhysRevD.94.111702

We review the electro-magnetic energy at axion haloscopes and find that the electric and the corresponding magnetic energy stored in the cavity modes or, equivalently, the mode dependent electric and magnetic form factors are the same regardless of the position of the cavity inside the solenoid. Furthermore, we extend our argument to the cases satisfying ⃗∇ ×⃗ ⃗Bexternal = 0, where ⃗Bexternal is a static magnetic field provided by a magnet at an axion haloscope. Two typical magnets, solenoidal and toroidal, satisfy ⃗∇ ×⃗ ⃗Bexternal = 0; thus, the electric and the corresponding magnetic energy stored in the cavity modes are always the same in both cases. The energy, however, is independent of the position of the cavity in axion haloscopes with a solenoid, and depends on those with a toroidal magnet.

I’ve given up on commenting on these popular science press articles.

In fact, I’ve given up on commenting on axions completely.

I’ve already said what I intend to say about them.

It’s all about detection and theory now.

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Do Dark Matter Axion Bose-Einstein Condensates Thermalize?

by Tommy on 21/01/2017

So looking around superficially I ran across this. I never really dug deeply into the BEC aspects of axions since I’m fairly familiar with the subject, but now I can see it’s a little more complicated than I thought. I never was a big fan of axion stars, though. Personally, I think that the deeper quantum field theory connections with the baryons prohibits that. That’s all to be developed.

Do Dark Matter Axions Form a Condensate with Long-Range Correlation?, Alan H. Guth, Mark P. Hertzberg and C. Prescod-Weinstein, Phys. Rev. D 92, 103513 (16 November 2015), DOI:10.1103/PhysRevD.92.103513, MIT-CTP 4625

Recently there has been significant interest in the claim that dark matter axions gravitationally thermalize and form a Bose-Einstein condensate with cosmologically long-range correlation. This has potential consequences for galactic scale observations. Here we critically examine this claim. We point out that there is an essential difference between the thermalization and formation of a condensate due to repulsive interactions, which can indeed drive long-range order, and that due to attractive interactions, which can lead to localized Bose clumps (stars or solitons) that only exhibit short range correlation. While the difference between repulsion and attraction is not present in the standard collisional Boltzmann equation, we argue that it is essential to the field theory dynamics, and we explain why the latter analysis is appropriate for a condensate. Since the axion is primarily governed by attractive interactions — gravitation and scalar-scalar contact interactions — we conclude that while a Bose-Einstein condensate is formed, the claim of long-range correlation is unjustified.

Of course with gravitational axions, all bets would be off concerning the excitation spectrum.

Regardless, this is an excellent introduction to the subject.

Ironically, this is when my adventure started.

I want this adventure to be over now.

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Cosmological Simulations of Running Vacuum Models Explored

by Tommy on 21/01/2017

I found this exposition to be moderately interesting.

Pairwise velocities in the “Running FLRW” cosmological model, Antonio Bibiano and Darren J. Croton (16 January 2017)

We present an analysis of the pairwise velocity statistics from a suite of cosmological N-body simulations describing the “Running Friedmann-Lemaître-Robertson-Walker” (R-FLRW) cosmological model. This model is based on quantum field theory in a curved space-time and extends ΛCDM with a time-evolving vacuum energy density ρΛ. To enforce local conservation of matter a time-evolving gravitational coupling is also included. Our results constitute the first study of velocities in the R-FLRW cosmology, and we also compare with other dark energy simulations suites, repeating the same analysis. We find a strong degeneracy between the pairwise velocity and σ8 at z = 0 for almost all scenarios considered, which remains even when we look back to epochs as early as z = 2. We also investigate various Coupled Dark Energy models, some of which show minimal degeneracy, and reveal interesting deviations from ΛCDM which could be readily exploited by future cosmological observations to test and further constrain our understanding of dark energy.

And for a bigger picture of the so called ‘multiverse’, there is this.

A Single Big Bang and Innumerable Similar Finite Observable Universe, Nilton Penha Silva, Accepted by Progress in Physics, Progress in Physics, 13, 2 (4 January 2017)

Gravity dominated Universe until it was 3.214 Gyr old and, after that, dark energy dominates leading to an eternal expansion, no matter if the Universe is closed, flat or open. That is the prediction of the expansion factor recently proposed by Silva. It is also shown that there is an upper limit for the size of the Observable Universe relative radial comoving coordinate, beyond which nothing is observed by our fundamental observer, on Earth. Our Observable Universe may be only a tiny portion of a much bigger Universe most of it unobservable to us. This leads to the idea that an endless number of other fundamental observers may live on equal number of Observable Universes similar to ours. An unique Big Bang originated an unique Universe, only part of it observable to us.

So take that, string theorists!

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A Credible Gauge Field Theory For My Cosmic QCD Axion

by Tommy on 20/01/2017

Thomas Applequist has always been ahead of the field. Or in this case, the curve.

SU(3) family gauge symmetry and the axion, Thomas Appelquist, Yang Bai and Maurizio Piai, Phys. Rev. D 75, 073005 (5 April 2007), doi:10.1103/PhysRevD.75.073005

We analyze the structure of a recently proposed effective field theory (EFT) for the generation of quark and lepton mass ratios and mixing angles, based on the spontaneous breaking of an SU(3) family gauge symmetry at a high scale F. We classify the Yukawa operators necessary to seed the masses, making use of the continuous global symmetries that they preserve. One global U(1), in addition to baryon number and electroweak hypercharge, remains unbroken after the inclusion of all operators required by standard model fermion phenomenology. An associated vacuum symmetry insures the vanishing of the first-family quark and charged-lepton masses in the absence of the family gauge interaction. If this U(1) symmetry is taken to be exact in the EFT, broken explicitly by only the QCD-induced anomaly, and if the breaking scale F is taken to lie in the range 109–1012 GeV, then the associated Nambu-Goldstone boson is a potential QCD axion.

This does seem to fit, but I will have to work through it since things have changed since then.

The Higgs boson and all that. This will take a while to work through.

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Distant Dwarf Galaxy Groups Confirm Dark Matter Dynamics

by Tommy on 19/01/2017

The observational astronomical evidence for dark matter particles continues to pile up.

This has been out for a week so now. I saw it repeated on Lawyer Herald of all places.

Direct evidence of hierarchical assembly at low masses from isolated dwarf galaxy groups, Sabrina Stierwalt, Sandra E. Liss, Kelsey E. Johnson, David R. Patton, George C. Privon, Gurtina Besla, Nitya Kallivayalil and Mary Putman, Accepted for Publication in Nature Astronomy (6 January 2017)

The demographics of dwarf galaxy populations have long been in tension with predictions from the Cold Dark Matter (CDM) paradigm. If primordial density fluctuations were scale-free as predicted, dwarf galaxies should themselves host dark matter subhaloes, the most massive of which may have undergone star formation resulting in dwarf galaxy groups. Ensembles of dwarf galaxies are observed as satellites of more massive galaxies, and there is observational and theoretical evidence to suggest that these satellites at z=0 were captured by the massive host halo as a group. However, the evolution of dwarf galaxies is highly susceptible to environment making these satellite groups imperfect probes of CDM in the low mass regime. We have identified one of the clearest examples to date of hierarchical structure formation at low masses: seven isolated, spectroscopically confirmed groups with only dwarf galaxies as members. Each group hosts 3-5 known members, has a baryonic mass of ~4.4 x 109 to 2 x 1010 Msun, and requires a mass-to-light ratio of <100 to be gravitationally bound. Such groups are predicted to be rare theoretically and found to be rare observationally at the current epoch and thus provide a unique window into the possible formation mechanism of more massive, isolated galaxies.

Be careful, Lawyer Herald will lock up your web browser!

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Axion Astronomy for New Microwave Haloscopes Simulated

by Tommy on 19/01/2017

Now that I know that the gravitational axion will soon be detected, next up is axion astronomy.

Of course, very course grained optical axion astronomy is already being routinely performed.

Axion astronomy with microwave cavity experiments, Ciaran A. J. O’Hare and Anne M. Green (11 January 2017)

Terrestrial searches for the conversion of dark matter axions or axion-like particles into photons inside magnetic fields are sensitive to the phase space structure of the local Milky Way halo. We simulate signals in a hypothetical future experiment based on the Axion Dark Matter eXperiment (ADMX) that could be performed once the axion has been detected and a frequency range containing the axion mass has been identified. We develop a statistical analysis to extract astrophysical parameters, such as the halo velocity dispersion and laboratory velocity, from such data and find that with only a few days integration time a level of precision can be reached matching that of astronomical observations. For longer experiments lasting up to a year in duration we find that exploiting the modulation of the power spectrum in time allows accurate measurements of the Solar peculiar velocity with an accuracy that would improve upon astronomical observations. We also simulate signals based on results from N-body simulations and find that finer substructure in the form of tidal streams would show up prominently in future data, even if only a subdominant contribution to the local dark matter distribution. In these cases it would be possible to reconstruct all the properties of a dark matter stream using the time and frequency dependence of the signal. Finally we consider the detection prospects for a network of streams from tidally disrupted axion miniclusters. These features appear much more prominently in the resolved spectrum than suggested by calculations based on a scan over a range of resonant frequencies, making the detection of axion minicluster streams more viable than previously thought. These results confirm that haloscope experiments in a post-discovery era are able to perform “axion astronomy”.

This article also contains a concise mathematical exposition of axion to photon conversion.

No Comments

The Reduced Charge Transfer Gap in the Multilayer Cuprates

by Tommy on 18/01/2017

This straightforward analysis solves the multilayer problem of the cuprates.

Relationship between the parent charge transfer gap and maximum transition temperature in cuprates, Wei Ruan, Cheng Hu, Jianfa Zhao, Peng Cai, Yingying Peng, Cun Ye, Runze Yu, Xintong Li, Zhenqi Hao, Changqing Jin, Xingjiang Zhou, Zheng-Yu Weng and Yayu Wang (17 January 2017)

One of the biggest puzzles concerning the cuprate high temperature superconductors is what determines the maximum transition temperature (Tc,max), which varies from less than 30 K to above 130 K in different compounds. Despite this dramatic variation, a robust trend is that within each family, the double-layer compound always has higher Tc,max than the single-layer counterpart. Here we use scanning tunneling microscopy to investigate the electronic structure of four cuprate parent compounds belonging to two different families. We find that within each family, the double layer compound has a much smaller charge transfer gap size (ΔCT), indicating a clear anticorrelation between ΔCT and Tc,max. These results suggest that the charge transfer gap plays a key role in the superconducting physics of cuprates, which shed important new light on the high Tc mechanism from doped Mott insulator perspective.

No Comments

Anomalous Transport with Non-Abelian Berry Curvature

by Tommy on 18/01/2017

This generalization is proving to be quite useful.

Kinetic Theory and Anomalous Transports in the Presence of Nonabelian Phase-Space Berry Curvatures, Tomoya Hayata and Yoshimasa Hidaka (15 January 2017)

We construct the kinetic theory in (1+2d)-dimensional phase space and time when all abelian and nonabelian phase-space Berry curvatures are nonzero. Then we calculate anomalous transports induced by the Berry curvatures on the basis of the kinetic theory. As an example, we study anomalous charge and spin transports induced by the SU(2) Berry curvatures. We also derive the topological effective theory to reproduce the transports in insulators calculated from the kinetic theory. Such an effective theory is given by the nonabelian phase space Chern-Simons theory.

No Comments

Topological Insulator Surface States Disentangled from the Bulk

by Tommy on 17/01/2017
Magneto Infrared Spectroscopy Faraday Rotation Topological Insulators

Magneto Infrared Spectroscopy Faraday Rotation Topological Insulators

Faraday rotation due to surface states in the topological insulator (Bi1−xSbx)2Te3, Yinming Shao, Kirk W. Post, Jhih-Sheng Wu, Siyuan Dai, Alex J. Frenzel, Anthony R. Richardella, Joon Sue Lee, Nitin Samarth, Michael M. Fogler, Alexander V. Balatsky, Dmitri E. Kharzeev and D. N. Basov, Nano Lett. (29 December 2016)

Using magneto-infrared spectroscopy, we have explored the charge dynamics of (Bi,Sb)2Te3 thin films on InP substrates. From the magneto-transmission data we extracted three distinct cyclotron resonance (CR) energies that are all apparent in the broad band Faraday rotation (FR) spectra. This comprehensive FR-CR data set has allowed us to isolate the response of the bulk states from the intrinsic surface states associated with both the top and bottom surfaces of the film. The FR data uncovered that electron- and hole-type Dirac fermions reside on opposite surfaces of our films, which paves the way for observing many exotic quantum phenomena in topological insulators.

These the million dollar takeaway quotes.

This hypothesis has implications for the finite frequency response of a TI: a resonance mode can be anticipated in infrared frequencies, offering yet another opportunity to investigate the condensed matter manifestations of phenomena discussed in high energy physics. The search for such resonances remains a challenge for future theoretical and experimental studies of 3D-TIs as well as Dirac/Weyl semimetals in magnetic field.

Such separated n- and p-type Dirac fermions paves the way for the observation of exotic quantum phenomena in TI, such as topological magneto-electric effect and topological exciton condensation.

In other words, this paves the way to solid state axion production, emission and detection.

No Comments

ARPES Investigation Demonstrates Nontrivial Bismuth Topology

by Tommy on 17/01/2017

The world is starting to wake up to the possibilities of bismuth, apparently.

Proving Nontrivial Topology of Pure Bismuth by Quantum Confinement, S. Ito, B. Feng, M. Arita, A. Takayama, R.-Y. Liu, T. Someya, W.-C. Chen, T. Iimori, H. Namatame, M. Taniguchi, C.-M. Cheng, S.-J. Tang, F. Komori, K. Kobayashi, T.-C. Chiang and I. Matsuda, Phys. Rev. Lett. 117, 236402 (2 December 2016), doi:10.1103/PhysRevLett.117.236402

The topology of pure Bi is controversial because of its very small (∼10 meV) band gap. Here we perform high-resolution angle-resolved photoelectron spectroscopy measurements systematically on 14−202 bilayers Bi films. Using high-quality films, we succeed in observing quantized bulk bands with energy separations down to ∼10 meV. Detailed analyses on the phase shift of the confined wave functions precisely determine the surface and bulk electronic structures, which unambiguously show nontrivial topology. The present results not only prove the fundamental property of Bi but also introduce a capability of the quantum-confinement approach.

Or rather, finally.

No Comments

Dark Matter Halos are Capable of Stripping Galaxies of Gas

by Tommy on 17/01/2017

This result clearly indicates the particulate nature of dark matter axions.

This doesn’t bode well for modified gravity theories of dark matter.

Cold gas stripping in satellite galaxies: from pairs to clusters, Toby Brown, Barbara Catinella, Luca Cortese, Claudia del P. Lagos, Romeel Dave, Virginia Kilborn, Martha P. Haynes, Riccardo Giovanelli and Mika Rafieferantsoa, MNRAS, 466, 2, 1275-1289 (16 January 2017) doi:10.1093/mnras/stw2991

In this paper we investigate environment driven gas depletion in satellite galaxies, taking full advantage of the atomic hydrogen (HI) spectral stacking technique to quantify the gas content for the entire gas-poor to -rich regime. We do so using a multi-wavelength sample of 10,600 satellite galaxies, selected according to stellar mass (log M/M ≥ 9) and redshift (0.02 ≤ z ≤ 0.05) from the Sloan Digital Sky Survey, with HI data from the Arecibo Legacy Fast ALFA (ALFALFA) survey. Using key HI-to-stellar mass scaling relations, we present evidence that the gas content of satellite galaxies is, to a significant extent, dependent on the environment in which a galaxy resides. For the first time, we demonstrate that systematic environmental suppression of gas content at both fixed stellar mass and fixed specific star formation rate (sSFR) in satellite galaxies begins in halo masses typical of the group regime (log Mh/M < 13.5), well before galaxies reach the cluster environment. We also show that environment driven gas depletion is more closely associated to halo mass than local density. Our results are then compared with state-of-the-art semi-analytic models and hydrodynamical simulations and discussed within this framework, showing that more work is needed if models are to reproduce the observations. We conclude that the observed decrease of gas content in the group and cluster environments cannot be reproduced by starvation of the gas supply alone and invoke fast acting processes such as ram-pressure stripping of cold gas to explain this.

See also:

xGASS: Gas-rich central galaxies in small groups and their connections to cosmic web gas feeding, Steven Janowiecki, Barbara Catinella, Luca Cortese, Amélie Saintonge, Toby Brown and Jing Wang, Accepted to MNRAS (6 January 2017)

We use deep HI observations obtained as part of the extended GALEX Arecibo SDSS survey (xGASS) to study the cold gas properties of central galaxies across environments. We find that, below stellar masses of 1010.2 M, central galaxies in groups have an average atomic hydrogen gas fraction ~ 0.3 dex higher than those in isolation at the same stellar mass. At these stellar masses, group central galaxies are usually found in small groups of N = 2 members. The higher HI content in these low mass group central galaxies is mirrored by their higher average star formation activity and molecular hydrogen content. At larger stellar masses, this difference disappears and central galaxies in groups have similar (or even smaller) gas reservoirs and star formation activity compared to those in isolation. We discuss possible scenarios able to explain our findings and suggest that the higher gas content in low mass group central galaxies is likely due to contributions from the cosmic web or HI-rich minor mergers, which also fuel their enhanced star formation activity.

ICRAR Press Release:

News Corp Australia Network Story

Probing the Cosmic Blobs.

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The Ground State and Excitation Spectrum of Quantum Bosons

by Tommy on 16/01/2017

This speaks volumes on the fundamental nature of dark matter axions as quantum bosons.

Emergent orders for bosonic atoms with competing short- and global-range interactions in an optical lattice, Renyuan Liao (13 January 2017)

We consider bosonic atoms loaded into optical lattices with cavity-mediated infinite-range interactions. Competing short- and global-range interactions cultivates a rich phase diagram. With a systematic field-theoretical perspective, we present an analytical construction of global ground-state phase diagram. We derive an effective theory describing compressible superfluid and supersolid states. We show that global-range interactions enhances density fluctuations and tunneling.

See also:;

Bose-Einstein condensates in the presence of Weyl spin-orbit coupling, Ting Wu and Renyuan Liao, New Journal of Physics, 19, 13008 (11 January 2017), doi:10.1088/1367-2630/aa559b

We consider two-component Bose-Einstein condensates subject to Weyl spin-orbit coupling. We obtain mean-field ground state phase diagram by variational method. In the regime where interspecies coupling is larger than intraspecies coupling, the system is found to be fully polarized and condensed at a finite momentum lying along the quantization axis. We characterize this phase by studying the excitation spectrum, the sound velocity, the quantum depletion of condensates, the shift of ground state energy, and the static structure factor. We find that spin-orbit coupling and interspecies coupling generally leads to competing effects.

It’s all good now.

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Quantum Cosmology PhD Thesis of Andre Franca at Munich

by Tommy on 14/01/2017

This is very much a must read PhD thesis and the best I have seen for some time now.

Quantum Many-Body Effects in Gravity and Bosonic Theories, Andre Franca, PhD Thesis Dissertation, Ludwig Maximilian University of Munich, Giorgi Dvali, Advisor (13 July 2016)

Many-body quantum effects play a crucial role in many domains of physics, from condensed matter to black-hole evaporation. The fundamental interest and difficulty in studying this class of systems is the fact that their effective coupling constant become rescaled by the number of particles involved g = αN, and thus we observe a breakdown of perturbation theory even for small values of the 2 → 2 coupling constant. We will study three very different systems which share the property that their behaviour is dominated by non-perturbative effects. The strong CP problem – the problem of why the ϴ angle of QCD is so small – can be solved by the Peccei-Quinn mechanism, which promotes the ϴ angle to a physical particle, the axion. The essence of the PQ mechanism is that the coupling will generate a mass gap, and thus the expectation value of the axion will vanish at the vacuum. It has been suggested that topological effects in gravity can spoil the axion solution. By using the dual formulation of the Peccei-Quinn mechanism, we are able to show that even in the presence of such dangerous contributions from gravity, the presence of light neutrinos can stabilize the axion potential. This effect also puts an upper bound on the lightest neutrino mass. We know that at high energies, gravitational scattering is dominated by black-hole formation. The typical size of black-holes is a growing function of the total center-of-mass energy involved in the scattering process. In the asymptotic future, these black-holes will decay into Hawking radiation, which has a typical wave-length of the size of the black-hole. Thus high energy gravitational scattering is dominated by low energy out states. It has been suggested that gravity is self-complete due to this effect, and that furthermore, there is a class of bosonic theories which can also be self-complete due to the formation of large classical field configurations: UV completion by Classicalization. We explore the idea of Classicalization versus Wilsonian UV completion in derivatively coupled scalars. We seek to answer the following question: how does the theory decide which road to take at high energies? We find out that the information about the high energy behaviour of the theory is encoded in the sign of the quartic derivative coupling. There is one sign that allows for a consistent Wilsonian UV-completion, and another sign that contains continuous classical field configurations for localized sources.

In the third part of the thesis we explore non-perturbative properties of black holes. We consider the model proposed by Dvali and Gomez where black holes are described as Bose-Einstein condensates N gravitons. These gravitons are weakly interacting, however their collective coupling constant puts them exactly at the critical point of a quantum phase transition αN = 1. We focus on a toy model which captures some of the features of information storage and processing of black holes. The carriers of information and entropy are the Bogoliubov modes, which we are able to map to pseudo-Goldstone bosons of a broken SU(2) symmetry. At the quantum phase transition this gap becomes 1/N, which implies that the cost of information storage disappears in the N → ∞ limit. Furthermore, the storage capacity and lifetime of the modes increases with N, becoming infinite in the N → ∞ limit. The attractive Bose gas which we considered is integrable in 1+1d. All the eigenstates of the system can be constructed using the Bethe ansatz, which transforms the Hamiltonian eigenvalue problem into a set of algebraic equations – the Bethe equations – for N parameters which play the role of generalize momenta. While the ground state and excitation spectrum are known in the repulsive regime, in the attractive case the system becomes more complicated due to the appearance of bound states. In order to solve the Bethe equations, we restrict ourselves to the N → ∞ limit and transform the algebraic equations into a constrained integral equation. By solving this integral equation, we are able to study the phase transition from the point of view of the Bethe ansatz. We observe that the phase transition happens precisely when the constraint is saturated, and manifests itself as a change in the functional form of the density of momenta. Furthermore, we are able to show that the ground state of this system can be mapped to the saddle-point equation of 2-dimensional Yang–Mills on a sphere, with a gauge group U(N).

Suffice it to say it will take me some time to work through these last two papers.

But unfortunately, I’m committed to this thing now.

Quantum gravity gauge field theory.

What a mess this is.

Update: Andre Franca is much smarter than his advisors and professors, and they know that.

Andre is smarter than me too, but I’m also smart enough to know that.

This is a breakthroughy body of work I don’t have to do.

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Primordial Gravitational Axion Gauge Field Cosmology Probed

by Tommy on 14/01/2017

These are long and complicated but state of the art precision cosmological arguments here.

Tensor Adiabatic Modes and Consistency Relations with Primordial Axion-Gauge Fields, Azadeh Maleknejad, Prepared for Submission to the Journal of High Energy Physics (JHEP)
(17 December 2016)

We study the tensor consistency relation in models of axion inflation with an SU(2) gauge field. In the tensor sector, we have two spin-2 modes, the standard gravity waves and the tensor perturbations of the SU(2) gauge field which sources the gravity waves at the linear level. Interestingly enough, we find that the gravity waves are adiabatic and Maldacena’s consistency relation including a long wavelength gravity wave holds in this setup. However, since it is partially polarized, there is a difference between the (n+1)-point functions with different helicity states proportional to the ratio of the gauge field density to the total density. These chiral n-point functions are the imprints of the SU(2) gauge field on the primordial cosmological perturbations and a robust observational feature of their contribution to the physics of inflation.

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Dark Matter BEC Halos Compared To Galaxy Rotation Rates

by Tommy on 12/01/2017

This seems fairly definitive.

Bose-Einstein Condensate Dark Matter Halos confronted with galactic rotation curves, M. Dwornik, Z. Keresztes, E. Kun and L. A. Gergely, Institute of Physics, University of Szeged, Dom Ter 9, Szeged 6720, Hungary (29 October 2016)

We present a comparative confrontation of both the Bose-Einstein Condensate (BEC) and the Navarro-Frenk-White (NFW) dark halo models with galactic rotation curves. We conclude that the BEC model fits better the dwarf galaxy dark matter distribution, but suffers from sharp cut-off in larger galaxies, where the NFW model performs better. In more detail, we employ High Surface Brightness (HSB), Low Surface Brightness (LSB) and dwarf galaxies with rotation curves falling into two classes, based on their shapes. In the first class the rotational velocities increase with radius over the whole observed range, the BEC and NFW models giving comparable fits for both HSB and LSB galaxies, while significantly improving over the NFW fit for dwarf galaxies. This improvement is due to the central density cusp avoidance property of the BEC model. The rotational velocity of HSB and LSB galaxies falling into the second class exhibit long at plateaus, resulting in a better fit of the NFW model for HSB galaxies, and comparable fits for LSB galaxies. The weaker performance of the BEC model for the HSB type II galaxies is due to the BEC density profiles dropping rapidly to zero outside a nearly constant density core. The investigated galaxy sample obeys the Tully-Fisher relation, including the particular characteristics exhibited by dwarf galaxies. We also show that in both dark matter models the fitting enforces a relation between the dark matter parameters: the characteristic density scales inversely with the corresponding characteristic distance.

So its basically game over for everything except the microwave axion.

Only the string theory community is holding this up now.

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