Penetrating But Not Yet Definitive Probe of Strontium Ruthenate

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

Strontium Ruthenate Under Strain

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

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

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

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

See also:

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

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

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

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Particulate Cold Dark Matter Found By Galactic Cluster Lensing

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

Dark Matter Galactic Cluster Lensing

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

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

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

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

Yale University Press Release

Take that, Harvard!

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Collective Modes and Defects Implicated in Phase Transitions

by Tommy on 25/02/2017

Here is yet another brilliant study.

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

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

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Frenkel Phonon Theory of Liquid Thermodynamics Developed

by Tommy on 24/02/2017

This qualifies as a landmark study.

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

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

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Analytic and Numerical Ab Initio Analysis of Hydrogen Bilayers

by Tommy on 24/02/2017

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

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

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

This work is of extremely high quality.

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

by Tommy on 19/02/2017

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

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

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

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

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

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

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

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

In a word – amorphization.

My new favorite word.

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

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

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

Update 3: It has begun.

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

High Pressure Amorphization of Bi4I4 – Bi+ Formation and Superconductivity

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

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

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

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

Quantum Gravity Gauge Field Theory

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

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

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

I hate axions. They follow me everywhere.

The gravity on this planet is heavy.

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New Haloscope Searches For Dark Matter Axions Proposed

by Tommy on 18/02/2017

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

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

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

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

You’ll be hearing that for a while too.

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The High Pressure Superconductivity of β-Bi4I4 Bismuth Iodide

by Tommy on 17/02/2017

So I will leave you with this last interesting tidbit.

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

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

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

See also:

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

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

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

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

Amorphization of a polymer?

Very suspicious.

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

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

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

It won’t be long now, trust me.

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Mathematical Description of Bulk Boundary Correspondances

by Tommy on 5/02/2017

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

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

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

There are some very interesting physical ramifications here too.

Happy Groundhog’s Day! Again.

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The Origin of Life from Non-Equilibrium Thermodynamics

by Tommy on 1/02/2017

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

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

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

More is better, I say.

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

by Tommy on 29/01/2017

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

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

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

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

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

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

See also:

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

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

See also also:

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

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

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

The Scientific Reports article is open. Enjoy!

Is my axion adventure over now?

You tell me. I wanna know.

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Quantum Cosmology as Condensed Matter Physics Catches On

by Tommy on 28/01/2017

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

‘Nothing’ and the universe

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

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

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

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

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

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

In my case, they need to be written first.

Dark Matter Vixens From Venus.

Macho Wimps are outraged.

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Historical Development of ΛCDM and Dark Matter Discussed

by Tommy on 28/01/2017

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

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

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

Let me show you how newbie is said properly.


You have your path.

I have mine.

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Isaac Silvera Manages to Finally Smush Hydrogen to a Metal

by Tommy on 27/01/2017

Here are some cool numbers for you.

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

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

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

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

Update 2: Eremets et al. checks in.

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

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

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

It won’t take this much effort.

I want a third opinion.

Update 3: Yet another published dissenting opinion.

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

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

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

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

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

Update 5: And finally, this devastating comeback.

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

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

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

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

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The Microscopic Mechanism of Superconductivity in FeSe

by Tommy on 27/01/2017

Behold the spectroscopic microscopic mechanism theory era of superconductivity.

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

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

The microspectroscopic era.

See also:

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

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

Now extend that microscopic theory into this.

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Electromagnetic Energy in Axion Haloscopes and Cavities

by Tommy on 23/01/2017

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

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

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

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

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

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

It’s all about detection and theory now.

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Do Dark Matter Axion Bose-Einstein Condensates Thermalize?

by Tommy on 21/01/2017

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

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

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

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

Regardless, this is an excellent introduction to the subject.

Ironically, this is when my adventure started.

I want this adventure to be over now.

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Cosmological Simulations of Running Vacuum Models Explored

by Tommy on 21/01/2017

I found this exposition to be moderately interesting.

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

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

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

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

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

So take that, string theorists!

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A Credible Gauge Field Theory For My Cosmic QCD Axion

by Tommy on 20/01/2017

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

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

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

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

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

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Distant Dwarf Galaxy Groups Confirm Dark Matter Dynamics

by Tommy on 19/01/2017

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

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

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

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

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

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Axion Astronomy for New Microwave Haloscopes Simulated

by Tommy on 19/01/2017

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

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

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

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

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

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The Reduced Charge Transfer Gap in the Multilayer Cuprates

by Tommy on 18/01/2017

This straightforward analysis solves the multilayer problem of the cuprates.

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

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

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Anomalous Transport with Non-Abelian Berry Curvature

by Tommy on 18/01/2017

This generalization is proving to be quite useful.

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

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

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Topological Insulator Surface States Disentangled from the Bulk

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

Magneto Infrared Spectroscopy Faraday Rotation Topological Insulators

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

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

These the million dollar takeaway quotes.

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

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

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

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ARPES Investigation Demonstrates Nontrivial Bismuth Topology

by Tommy on 17/01/2017

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

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

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

Or rather, finally.

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Dark Matter Halos are Capable of Stripping Galaxies of Gas

by Tommy on 17/01/2017

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

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

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

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

See also:

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

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

ICRAR Press Release:

News Corp Australia Network Story

Probing the Cosmic Blobs.

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The Ground State and Excitation Spectrum of Quantum Bosons

by Tommy on 16/01/2017

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

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

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

See also:;

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

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

It’s all good now.

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Quantum Cosmology PhD Thesis of Andre Franca at Munich

by Tommy on 14/01/2017

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

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

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

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

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

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

Quantum gravity gauge field theory.

What a mess this is.

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

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

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

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Primordial Gravitational Axion Gauge Field Cosmology Probed

by Tommy on 14/01/2017

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

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

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

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Dark Matter BEC Halos Compared To Galaxy Rotation Rates

by Tommy on 12/01/2017

This seems fairly definitive.

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

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

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

Only the string theory community is holding this up now.

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Dense, Strongly Coupled and Correlated Exciton Condensation

by Tommy on 11/01/2017

I’ve been reporting on exciton plasma physics for a while here.

Here is something that may directly apply to dark matter as well.

Condensation to a strongly correlated dark fluid of two dimensional dipolar excitons, Yotam Mazuz-Harpaz, Kobi Cohen and Ronen Rapaport (10 January 2017)

Recently we reported on the condensation of cold, electrostatically trapped dipolar excitons in GaAs bilayer heterostructure into a new, dense and dark collective phase. Here we analyze and discuss in detail the experimental findings and the emerging evident properties of this collective liquid-like phase. We show that the phase transition is characterized by a sharp increase of the number of non-emitting dipoles, by a clear contraction of the fluid spatial extent into the bottom of the parabolic-like trap, and by spectral narrowing. We extract the total density of the condensed phase which we find to be consistent with the expected density regime of a quantum liquid. We show that there are clear critical temperature and excitation power onsets for the phase transition and that as the power further increases above the critical power, the strong darkening is reduced down until no clear darkening is observed. At this point another transition appears which we interpret as a transition to a strongly repulsive yet correlated eh plasma. Based on the experimental findings, we suggest that the physical mechanism that may be responsible for the transition is a dynamical final-state stimulation of the dipolar excitons to their dark spin states, which have a long lifetime and thus support the observed sharp increase in density. Further experiments and modeling will hopefully be able to unambiguously identify the physical mechanism behind these recent observations.

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QCD and Electroweak Vacuum θ-Term Axion Angle Inheritance

by Tommy on 9/01/2017

This is exactly what I was looking for!

(In)dependence of Theta in the Higgs Regime without Axions, Mikhail Shifman and Arkady Vainshtein (2 January 2017)

We revisit the issue of the vacuum angle theta dependence in weakly coupled (Higgsed) Yang-Mills theories. Two most popular mechanisms for eliminating physical theta dependence are massless quarks and axions. Anselm and Johansen noted that the vacuum angle θ, associated with the electroweak SU(2) in the Glashow-Weinberg-Salam model, is unobservable although all fermion fields obtain masses through Higgsing and there is no axion. We generalize this idea to a broad class of Higgsed Yang-Mills theories.

In the second part we consider consequences of Grand Unification. We start from a unifying group, e.g. SU(5), at a high ultraviolet scale and evolve the theory down within the Wilson procedure. If on the way to infrared the unifying group is broken down into a few factors, all factor groups inherit one and the same theta angle – that of the unifying group. We show that embedding the SM in SU(5) drastically changes the Anselm-Johansen conclusion: the electroweak vacuum angle θEW, equal to θQCD becomes in principle observable in ∆B = ∆L

See also:

Can Electro-Weak θ-Term be Observable?, A. A. Anselm and A. A.Johansen (14 May 1993)

We rederive and discuss the result of the previous paper that in the standard model θ-term related to W-boson field can not be induced by weak instantons. This follows from the existence of the fermion zero mode in the instanton field even when Yukawa couplings are switched on and there are no massless particles. We consider the new index theorem connecting the topological charge of the weak gauge field with the number of fermion zero modes of a certain differential operator which depends not only on gauge but also on Higgs fields. The possible generalizations of the standard model are discussed which lead to nonvanishing weak θ-term. In SU(2)L × SU(2)R model the θ dependence of the vacuum energy is computed.

Ok then! Off we go. I feel I am onto something now.

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Monoverse, Multiverse or Universe? Pick Any Two of Three.

by Tommy on 8/01/2017

So I finished up part one of the quantum cosmology essay, and then I ran across this meme.

I’m not sure who specifically thought that one up, but I can at least stop speculating for a while since I have now written down parts of the tangled web I have woven for myself since I simply tried to find a ZT=3 thermoelectric device a year or more ago now. In retrospect, I probably should have stuck with that. It was doing well even before the axion suddenly announced its dramatic appearance in my world of condensed matter physics. This is always serendipitous.

In the interim, I have solved the origin of life problem, which James Crutchfield promptly proved mathematically, then I went on to outline a new hypothesis for dark matter. And then I created an entire new branch of physics, quantum cosmology, from what I learned from my axion research experience. Now I am stuck with it. It needs to become mathematics. And even worse, before I can do that, I need to physically detect it, and then take a look at some of its physical properties.

Beyond its apparent effective particle mass.

I’m screwed. I’m totally screwed. I hate axions.

Gravitational Axions in Quantum Gravity and Cosmology

Gravitational Axions as Dark Matter

Remember to buy my book!

Tommy. The Legend.

In his own mind.

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Desperate MACHO WIMPs Plead For More Dark Matter Pork

by Tommy on 7/01/2017

I could see this coming light years away.

Dark Matter Overview, N. Fornengo, XXV ECRS 2016 Proceedings, eConf C16-09-04.3 (3 January 2017)

Identification of a solution to the dark matter problem has many arrows to its bow: if dark matter is a new elementary particle, both laboratory experiments and astrophysics can bring relevant and complementary pieces of information, that than can be confronted and composed to solve this intriguing puzzle. Although we currently do not have a unique and obvious target for the DM particle, we can rely on a broad range of ideas, tools and methods that make the investigation of dark matter a multi-frequency, multi-messenger and multi-techniques integrated endeavour.

We have BOTH kinds here, Dark Money AND Black Money.

Mo money, mo money, mo money!

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Dark Matter Gravitational Axions in Quantum Cosmology

by Tommy on 5/01/2017

Ok, so I had to whack pages of essay and brain storming after I recovered from the holidays.

Gravitational Axions in Quantum Gravity and Cosmology

So I looked it up and it turns out some other guy already invented it, a loop gravity guy.

But what about the Little Bounce Model. I still get that one, right?

A hypothesis was proposed for cosmic QCD axions as gravitational bosons within quantum gravity; physical gravitational analogues of Goldstone bosons coupled to artificial Higgs mode excitations as known in condensed matter physics systems; essentially low mass, low frequency and low temperature bosons of either a single species, a distribution of particle mass, or spectrum of particle mass coupling. The masses of the hypothetical dark matter particles are expected to be in the microwave region and therefore it’s possible the boson itself could be a mass mediator akin to a gravitational gauge boson.

Extending these concepts to spacetime and gravitation, and thus cosmic axions and the quantization of gravitational forces and fields, quantum gravity, involves introducing the concepts of geometry and topology from condensed matter physics analogue systems for reference, into quantum cosmology.

The purpose of this essay is to delve deeper into these new speculative quantum cosmologies based upon these concepts. Specifically I will discuss the novel concepts of axion fa field dependencies, and microwave axions as electromagnetic mass mediators within infrared and optical state transitions.

That’s puttin it out there, right? I don’t want to go full on crackpot.

It will be a while before this goes live.

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