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.

https://arxiv.org/abs/gr-qc/0101003

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

http://www.imperial.ac.uk/media/imperial-college/research-centres-and-groups/theoretical-physics/msc/dissertations/2010/Michael-Patrick-Cooke-Dissertation.pdf

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.

http://lifeform.net/archimedes/Cosmic_Axions.pdf

No Comments

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.

http://www.pnas.org/content/early/2017/05/10/1701562114

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.

No Comments

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.

https://arxiv.org/abs/1703.00543

https://journals.aps.org/prd/abstract/10.1103/PhysRevD.95.103504

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.

No Comments

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!

https://arxiv.org/abs/1705.05841

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.

No Comments

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.

https://arxiv.org/abs/1705.06269

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.

http://lifeform.net/archimedes/Cosmic_Evolution.pdf

The Cosmic Evolution of Autobiogenesis

No Comments

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

by Tommy on 17/05/2017

Grok and you shall know.

https://arxiv.org/abs/1705.05692

http://advances.sciencemag.org/content/3/4/e1602372

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.

No Comments

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.

https://arxiv.org/abs/1705.05378

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?

No Comments

Generalized Lieb-Schultz-Mattis Theorems for SPT Phases

by Tommy on 16/05/2017

I feel a major generalization ‘coming on.

https://arxiv.org/abs/1705.04691

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.

No Comments

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.

https://arxiv.org/abs/1705.04027

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.

No Comments

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.

https://arxiv.org/abs/1705.03892

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: https://arxiv.org/abs/1705.00012

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.

No Comments

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.

https://arxiv.org/abs/1705.03905

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.

No Comments

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.

http://science.sciencemag.org/content/356/6336/418

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!

No Comments

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?

https://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys4112.html

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.

No Comments

Room Temperature Biexcitons in Monolayer Tungsten Disulfide

by Tommy on 9/05/2017

This is like excitons in bismuth triiodide all over again.

https://arxiv.org/abs/1705.02943

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.

No Comments

Lattice QCD Topology Further Refines Axion Mass Range

by Tommy on 9/05/2017

https://arxiv.org/abs/1705.01847

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.

No Comments

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.

http://lifeform.net/archimedes/First_Light.pdf

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

http://www.xfel.eu/

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.

No Comments

Gapless Symmetry Protected Topological Matter Proposed

by Tommy on 5/05/2017

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

https://arxiv.org/abs/1705.01557

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.

No Comments

Topological Quantum Chemistry Becomes Predictive

by Tommy on 5/05/2017

https://arxiv.org/abs/1705.01617

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: https://arxiv.org/abs/1703.02050

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.

No Comments

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.

https://arxiv.org/abs/1612.04824

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.118.131101

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.

No Comments

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.

https://arxiv.org/abs/1705.00676

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.

No Comments

Cubic Reference Lattice of Bismuth Superconductivity Proposed

by Tommy on 4/05/2017

It looks like somebody already beat me to it.

https://arxiv.org/abs/1705.01506

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.

http://lifeform.net/archimedes/Bismuth_Iodide.pdf

This is coming whether you like it or not.

No Comments

Topoelectric RLC Circuit Simulation of Topological Semimetals

by Tommy on 3/05/2017

https://arxiv.org/abs/1705.01077

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.

No Comments

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.

https://arxiv.org/abs/1704.05258

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.

http://lifeform.net/archimedes/Bismuth.pdf

No Comments

I Wear the Crown of Science

by Tommy on 29/04/2017

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

No Comments

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.

https://arxiv.org/abs/1704.03814

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

https://arxiv.org/abs/1512.02694

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.

No Comments

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.

https://arxiv.org/pdf/1704.08149.pdf

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.

No Comments

Pressure Induced Superconductivity in Tantalum Ditelluride

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

Tantalum Ditelluride Phase Diagram

Here is something interesting.

https://arxiv.org/abs/1704.08106

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.

No Comments

Chern Simons Theory of Composite Fermions Developed

by Tommy on 26/04/2017

This is how one begins to do quantum cosmology.

https://arxiv.org/abs/1704.07712

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.

No Comments

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.

https://arxiv.org/abs/1704.07805

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

No Comments

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!

https://arxiv.org/abs/1704.07557

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?

No Comments

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.

https://arxiv.org/abs/1704.07742

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.

No Comments

Weyl Metals Reviewed

by Tommy on 26/04/2017

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

https://arxiv.org/abs/1704.06660

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.

No Comments

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.

https://arxiv.org/abs/1704.06991

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.

No Comments

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?

https://arxiv.org/abs/1610.06882

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.

No Comments

Happy Earth Day! Again.

by Tommy on 23/04/2017

Are we there yet?

No Comments