So there it is. This entire Trump administration is going to jail.
The Republican Party is complicit to sedition and treason.
So there it is. This entire Trump administration is going to jail.
The Republican Party is complicit to sedition and treason.
Authoritarians, American Fascists, and Traitors.
Murderers and Thieves. Liars for hire.
Assassins of Democracy.
I apologize for my rhetoric lately, I was having a constitutional crisis.
So unless there is some really big breakthrough, I will no longer be covering it.
I’m ok with where I am at with science right now, the origin of the universe and the origin of life.
The evolution of me, I’m up to date. Gravitational axions. They work for me.
And please accept my apologies, I lost my mind there for a while.
I’m good. Thanks for your consideration and patience.
I have some memoirs to write now.
Update 1: Paul Manafort, et al.
The memes have spoken.
Trump, Republicans, …
You get the picture.
Update 2: Devin Nunes, et al.
The picture gets clearer.
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: https://arxiv.org/abs/1703.05804
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.
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.
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.
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: https://arxiv.org/abs/1703.04321
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: https://arxiv.org/abs/1703.05491
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.
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.
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.
March 20, 2017, on CSPAN.
Be there or be square.
Update: Happy Pi Day!
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.
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.
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: https://arxiv.org/abs/1604.06669
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!
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
Take that, Harvard!
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.
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.
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.
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.
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.
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: https://arxiv.org/abs/1701.08860
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?
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.
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.
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.
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: http://arxiv.org/abs/1408.3614
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.
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.
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 www.origins.asu.edu 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.
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.
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.
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: https://arxiv.org/abs/1701.07728
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.
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.
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.
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!
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.
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!
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.
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.
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.