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Partial deconfinement at strong coupling on the lattice

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arXiv 2020年

作者： Watanabe, Hiromasa Bergner, Georg Bodendorfer, Norbert Funai, Shotaro Shiba Hanada, Masanori Rinaldi, Enrico Schäfer, Andreas Vranas, Pavlos Graduate School of Pure and Applied Sciences University of Tsukuba Tsukuba Ibaraki305-8571 Japan University of Jena Institute for Theoretical Physics Max-Wien-Platz 1 JenaD-07743 Germany University of Regensburg Institute of Theoretical Physics Universitätsstrasse 31 D-93053 Germany 1919-1 Tancha Onna-son Kunigami-gun Okinawa904-0495 Japan Department of Mathematics University of Surrey Guildford SurreyGU2 7XH United Kingdom Arithmer Inc. R&D Headquarters Minato Tokyo106-6040 Japan RIKEN iTHEMS Program Wako Saitama351-0198 Japan Nuclear and Chemical Sciences Division Lawrence Livermore National Laboratory LivermoreCA94550 United States Nuclear Science Division Lawrence Berkeley National Laboratory BerkeleyCA94720 United States

We provide evidence for partial deconfinement - the deconfinement of a SU(M) subgroup of the SU(N) gauge group - by using lattice Monte Carlo simulations. We take matrix models as concrete examples. By appropriately fixing the gauge, we observe that the M×M submatrices deconfine. This gives direct evidence for partial deconfinement at strong coupling. We discuss the applications to QCD and holography. Copyright © 2020, The Authors. All rights reserved.

关键词： Monte Carlo methods

High temperature structure detection in ferromagnets

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arXiv 2018年

作者： Cao, Yuan Neykov, Matey Liu, Han Program in Applied and Computational Mathematics Princeton University PrincetonNJ United States Department of Statistics & Data Science Carnegie Mellon University PittsburghPA United States Department of Electrical Engineering and Computer Science Northwestern University EvanstonIL United States

This paper studies structure detection problems in high temperature ferromagnetic (positive interaction only) Ising models. The goal is to distinguish whether the underlying graph is empty, i.e., the model consists of independent Rademacher variables, versus the alternative that the underlying graph contains a subgraph of a certain structure. We give matching upper and lower minimax bounds under which testing this problem is possible/impossible respectively. Our results reveal that a key quantity called graph arboricity drives the testability of the problem. On the computational front, under a conjecture of the computational hardness of sparse principal component analysis, we prove that, unless the signal is strong enough, there are no polynomial time linear tests on the sample covariance matrix which are capable of testing this problem. Copyright © 2018, The Authors. All rights reserved.

关键词： Ferromagnetism

Characterization of temporarily-captured minimoon 2020 CD3 by Keck time-resolved spectrophotometry

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arXiv 2020年

作者： Bolin, Bryce T. Fremling, Christoffer Holt, Timothy R. Hankins, Matthew J. Ahumada, Tomás Anand, Shreya Bhalerao, Varun Burdge, Kevin B. Copperwheat, Chris M. Coughlin, Michael Deshmukh, Kunal P. De, Kishalay Kasliwal, Mansi M. Morbidelli, Alessandro Purdum, Josiah N. Quimby, Robert Bodewits, Dennis Chang, Chan-Kao Ip, Wing-Huen Hsu, Chen-Yen Laher, Russ R. Lin, Zhong-Yi Lisse, Carey M. Masci, Frank J. Ngeow, Chow-Choong Tan, Hanjie Zhai, Chengxing Burruss, Rick Dekany, Richard Delacroix, Alexandre Duev, Dmitry A. Graham, Matthew Hale, David Kulkarni, Shrinivas R. Kupfer, Thomas Mahabal, Ashish Mróz, Przemyslaw J. Neill, James D. Riddle, Reed Rodriguez, Hector Smith, Roger M. Soumagnac, Maayane T. Walters, Richard Yan, Lin Zolkower, Jeffry Division of Physics Mathematics and Astronomy California Institute of Technology PasadenaCA91125 United States IPAC Mail Code 100-22 Caltech 1200 E. California Blvd. PasadenaCA91125 United States University of Southern Queensland Computational Engineering and Science Research Centre QLD Australia Southwest Research Institute Department of Space Studies BoulderCO80302 United States Department of Astronomy University of Maryland College ParkMD20742 United States Division of Physics Mathematics and Astronomy California Institute of Technology PasadenaCA91125 United States Department of Physics Indian Institute of Technology Bombay Powai Mumbai400076 India Astrophysics Research Institute Liverpool John Moores University 146 Brownlow Hill LiverpoolL3 5RF United Kingdom School of Physics and Astronomy University of Minnesota MinneapolisMN55455 United States Department of Metallurgical Engineering and Materials Science Indian Institute of Technology Bombay Powai Mumbai400076 India Université Côte d’Azur Observatoire de la Côte d’Azur CNRS Laboratoire Lagrange Boulevard de l’Observatoire CS 34229 Nice cedex 406304 France Department of Astronomy San Diego State University 5500 Campanile Dr San DiegoCA92182 United States University of Tokyo Institutes for Advanced Study University of Tokyo KashiwaChiba277-8583 Japan Physics Department Leach Science Center Auburn University AuburnAL36832 United States Institute of Astronomy National Central University 32001 Taiwan Johns Hopkins University Applied Physics Laboratory LaurelMD20723 United States Jet Propulsion Laboratory California Institute of Technology 4800 Oak Grove Drive PasadenaCA91109 United States Caltech Optical Observatories California Institute of Technology PasadenaCA91125 United States Kavli Institute for Theoretical Physics University of California Santa BarbaraCA93106 United States Center for Data Driven Discovery California Institute of Technology PasadenaCA

We present rotationally-averaged visible spectrophotometry of minimoon 2020 CD3, the second asteroid known to become temporarily captured by the Earth-Moon system’s gravitational field. The spectrophotometry was taken with Keck I/LRIS between wavelengths 434 nm and 912 nm in B, g, V, R, I and RG850 filters as it was leaving the Earth-Moon system on 2020 March 23 UTC. The broad-band spectrophotometry of 2020 CD3 most closely resembles the spectra of V-type asteroids and some Lunar rock samples with a reddish slope of ∼18%/100 nm between 434 nm and 761 nm corresponding to colors of g-r = 0.62±0.08, r-i = 0.21 ± 0.06 and an absorption band at ∼900 nm corresponding to i-z = -0.54±0.10 (DeMeo et al. 2009;Isaacson et al. 2011). Combining our measured 31.9±0.1 absolute magnitude with an albedo of 0.35 typical for V-type asteroids (DeMeo & Carry 2013), we determine 2020 CD3’s size to be ∼1.0±0.1 m making it the first minimoon and one of the smallest asteroids to be spectrally characterized. We use our time-series photometry to detect periodic lightcurve variations with a −4 false alarm probability corresponding to a lightcurve period of ∼573 s and a lightcurve amplitude of ∼1 mag implying 2020 CD3 possesses a b/a axial ratio of ∼2.5. In addition, we extend the observational arc of 2020 CD3 to 37 days between 2020 February 15 UTC and 2020 March 23 UTC. From the improved orbital solution for 2020 CD3, we estimate its likely duration of its capture to be ∼2 y, and we measure the non-gravitation perturbation on its orbit due to radiation pressure with an area-to-mass ratio of 6.9±2.4×10−4 m2/kg implying a density of 2.1±0.7 g/cm3, broadly compatible with the densities of other meter-scale asteroids (e.g., Micheli et al. 2012;Mommert et al. 2014) and Lunar rock (∼2.4 g/cm3, Kiefer et al. 2012). We searched for pre-discovery observations of 2020 CD3 in the ZTF archive as far back as 2018 October (Masci et al. 2019), but were unable to locate any positive detections. Copyright © 2

关键词： Asteroids

A variable high-order shock-capturing finite difference method with GP-WENO

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arXiv 2018年

作者： Reyes, Adam Lee, Dongwook Graziani, Carlo Tzeferacos, Petros Department of Physics University of California Santa CruzCA United States Department of Applied Mathematics University of California Santa CruzCA United States Flash Center for Computational Science Department of Astronomy & Astrophysics University of Chicago IL United States Mathematics and Computer Science Argonne National Laboratory ArgonneIL United States

We present a new finite difference shock-capturing scheme for hyperbolic equations on static uniform grids. The method provides selectable high-order accuracy by employing a kernel-based Gaussian Process (GP) data prediction method which is an extension of the GP high-order method originally introduced in a finite volume framework by the same authors. The method interpolates Riemann states to high order, replacing the conventional polynomial interpolations with polynomial-free GP-based interpolations. For shocks and discontinuities, this GP interpolation scheme uses a nonlinear shock handling strategy similar to Weighted Essentially Non-oscillatory (WENO), with a novelty consisting in the fact that nonlinear smoothness indicators are formulated in terms of the Gaussian likelihood of the local stencil data, replacing the conventional L2-type smoothness indicators of the original WENO method. We demonstrate that these GP-based smoothness indicators play a key role in the new algorithm, providing significant improvements in delivering high - and selectable - order accuracy in smooth flows, while successfully delivering non-oscillatory solution behavior in discontinuous flows. Copyright © 2018, The Authors. All rights reserved.

关键词： Gaussian distribution

The Atacama Cosmology Telescope: Constraints on Cosmic Birefringence

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arXiv 2020年

作者： Namikawa, Toshiya Guan, Yilun Darwish, Omar Sherwin, Blake D. Aiola, Simone Battaglia, Nicholas Beall, James A. Becker, Daniel T. Bond, J. Richard Calabrese, Erminia Chesmore, Grace E. Choi, Steve K. Sifón, Cristóbal Devlin, Mark J. Dunkley, Joanna Dünner, Rolando Fox, Anna E. Gallardo, Patricio A. Gluscevic, Vera Han, Dongwon Hasselfield, Matthew Hilton, Gene C. Hincks, Adam D. Hložek, Renée Hubmayr, Johannes Huffenberger, Kevin Hughes, John P. Koopman, Brian J. Kosowsky, Arthur Louis, Thibaut Lungu, Marius MacInnis, Amanda Madhavacheril, Mathew S. Mallaby-Kay, Maya Maurin, Loïc McMahon, Jeffrey Moodley, Kavilan Naess, Sigurd Nati, Federico Newburgh, Laura B. Nibarger, John P. Niemack, Michael D. Page, Lyman A. Qu, Frank J. Robertson, Naomi Schillaci, Alessandro Sehgal, Neelima Simon, Sara M. Spergel, David N. Staggs, Suzanne T. Storer, Emilie R. van Engelen, Alexander van Lanen, Jeff Wollack, Edward J. Department of Applied Mathematics and Theoretical Physics University of Cambridge Wilberforce Road CambridgeCB3 0WA United Kingdom Department of Physics and Astronomy University of Pittsburgh PittsburghPA15260 United States Center for Computational Astrophysics Flatiron Institute 162 5th Avenue New YorkNY10010 United States Department of Astronomy Cornell University IthacaNY14853 United States National Institute of Standards and Technology 325 Broadway BoulderCO80305 United States Canadian Institute for Theoretical Astrophysics University of Toronto TorontoONM5S 3H8 Canada School of Physics and Astronomy Cardiff University CardiffCF10 3AT United Kingdom Department of Physics University of Michigan Ann ArborMI48109 United States Department of Astronomy Cornell University IthacaNY14853 United States Instituto de Física Pontificia Universidad Católica de Valparaíso CasillaValparaíso4059 Chile Department of Physics and Astronomy University of Pennsylvania 209 South 33rd Street PhiladelphiaPA19104 United States Department of Astrophysical Sciences Princeton University 4 Ivy Lane PrincetonNJ08544 United States Joseph Henry Laboratories of Physics Jadwin Hall Princeton University PrincetonNJ08544 United States Instituto de Astrofísica Centro de Astro-Ingeniería Facultad de Física Pontificia Spain Universidad Católica de Chile Av. Vicuña Mackenna 4860 Macul Santiago7820436 Chile Department of Physics Cornell University IthacaNY14853 United States Department of Physics and Astronomy University of Southern California Los AngelesCA90089-0484 United States Physics and Astronomy Department Stony Brook University Stony BrookNY11794 United States Canadian Institute for Theoretical Astrophysics 60 St George St TorontoONM5S 3H8 Canada Dunlap Institute for Astronomy and Astrophysics University of Toronto 50 St George Street TorontoONM5S 3H4 Canada David A. Dunlap Department of Astronomy and Astrophysics University of Toronto 50

We present new constraints on anisotropic birefringence of the cosmic microwave background polarization using two seasons of data from the Atacama Cosmology Telescope covering 456 square degrees of sky. The birefringence power spectrum, measured using a curved-sky quadratic estimator, is consistent with zero. Our results provide the tightest current constraint on birefringence over a range of angular scales between 5 arcminutes and 9 degrees. We improve previous upper limits on the amplitude of a scale-invariant birefringence power spectrum by a factor of between 2 and 3. Assuming a nearly-massless axion field during inflation, our result is equivalent to a 2σ upper limit on the Chern-Simons coupling constant between axions and photons of gαγ −2/HI where HI is the inflationary Hubble scale. Copyright © 2020, The Authors. All rights reserved.

关键词： Birefringence

Evolution of electronic structure and electron-phonon coupling in ultrathin tetragonal CoSe films

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Physical Review Materials 2018年第11期2卷 114005-114005页

作者： L. Shen C. Liu F. W. Zheng X. Xu Y. J. Chen S. C. Sun L. Kang Z. K. Liu Q. K. Xue L. L. Wang Y. L. Chen L. X. Yang State Key Laboratory of Low Dimensional Quantum Physics Department of Physics Tsinghua University Beijing 100084 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China School of Physical Science and Technology CAS-Shanghai Science Research Center ShanghaiTech University Shanghai 201210 China Collaborative Innovation Center of Quantum Matter Beijing 100084 China Department of Physics Clarendon Laboratory University of Oxford Parks Road Oxford OX1 3PU United Kingdom

Two-dimensional materials have attracted considerable research attention recently due to their extraordinary physical and chemical properties. In this paper, we systematically investigate the electronic structure of ultrathin tetragonal CoSe films with different thicknesses that are isostructural to two-dimensional high-temperature superconductor FeSe using high-resolution angle-resolved photoemission spectroscopy, scanning tunneling microscopy, and ab initio calculation. Interestingly, the nonsymmorphic symmetry of the CoSe monolayer protects both exotic saddle band degeneracy and Dirac points, realizing two-dimensional Dirac fermions. Our temperature and film-thickness-dependent measurements reveal momentum-dependent electron-phonon coupling in CoSe films, which is enhanced with reduced film thickness. Moreover, the electronic states in the CoSe monolayer strongly couple to high-frequency phonons in the SrTiO3 substrate, similar to the situation in the FeSe monolayer. Our results not only present a platform to investigate the electronic properties in close vicinity of the high-temperature superconductor FeSe monolayer, but also shed light on the understanding of the coupling between two-dimensional materials and substrates beneath.

关键词： Electronic structure Superconductivity Surface & interfacial phenomena Interfaces Thin films Ultrathin films Angle-resolved photoemission spectroscopy Density functional theory Molecular beam epitaxy Scanning tunneling microscopy Scanning tunneling spectroscopy

Model reduction with memory and the machine learning of dynamical systems

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arXiv 2018年

作者： Ma, Chao Wang, Jianchun Weinan, E. Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States Department of Mechanics and Aerospace Engineering Southern University of Science and Technology Shenzhen518055 China Beijing Institute of Big Data Research Beijing100871 China

The well-known Mori-Zwanzig theory tells us that model reduction leads to memory effect. For a long time, modeling the memory effect accurately and efficiently has been an important but nearly impossible task in developing a good reduced model. In this work, we explore a natural analogy between recurrent neural networks and the Mori-Zwanzig formalism to establish a systematic approach for developing reduced models with memory. Two training models-a direct training model and a dynamically coupled training model-are proposed and compared. We apply these methods to the Kuramoto-Sivashinsky equation and the Navier-Stokes equation. Numerical experiments show that the proposed method can produce reduced model with good performance on both short-term prediction and long-term statistical properties. Copyright © 2018, The Authors. All rights reserved.

关键词： Recurrent neural networks

Analyses of protein cores reveal fundamental differences between solution and crystal structures

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arXiv 2019年

作者： Mei, Zhe Treado, John D. Grigas, Alex T. Levine, Zachary A. Regan, Lynne O'Hern, Corey S. Integrated Graduate Program in Physical & Engineering Biology Yale University New HavenCT06520 United States Department of Chemistry Yale University New HavenCT06520 United States Department of Mechanical Engineering & Materials Science Yale University New HavenCT06520 United States Graduate Program in Computational Biology & Bioinformatics Yale University New HavenCT06520 United States Department of Pathology Yale University New HavenCT06520 United States Department of Molecular Biophysics and Biochemistry Yale University New HavenCT06520 United States Institute of Quantitative Biology Biochemistry and Biotechnology Center for Synthetic and Systems Biology School of Biological Sciences University of Edinburgh Department of Physics Yale University New HavenCT06520 United States Department of Applied Physics Yale University New HavenCT06520 United States

There have been several studies suggesting that protein structures solved by NMR spectroscopy and x-ray crystallography show significant differences. To understand the origin of these differences, we assembled a database of high-quality protein structures solved by both methods. We also find significant differences between NMR and crystal structures|in the root-mean-square deviations of the Cα atomic positions, identities of core amino acids, backbone and sidechain dihedral angles, and packing fraction of core residues. In contrast to prior studies, we identify the physical basis for these differences by modelling protein cores as jammed packings of amino-acid-shaped particles. We find that we can tune the jammed packing fraction by varying the degree of thermalization used to generate the packings. For an athermal protocol, we find that the average jammed packing fraction is identical to that observed in the cores of protein structures solved by x-ray crystallography. In contrast, highly thermalized packing-generation protocols yield jammed packing fractions that are even higher than those observed in NMR structures. These results indicate that thermalized systems can pack more densely than athermal systems, which suggests a physical basis for the structural differences between protein structures solved by NMR and x-ray crystallography. Copyright © 2019, The Authors. All rights reserved.

关键词： X ray crystallography

Hypostatic jammed packings of frictionless nonspherical particles

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Physical Review E 2018年第1期97卷 012909-012909页

作者： Kyle VanderWerf Weiwei Jin Mark D. Shattuck Corey S. O'Hern Department of Physics Yale University New Haven Connecticut 06520 USA Department of Mechanics and Engineering Science Peking University Beijing 100871 China Department of Mechanical Engineering & Materials Science Yale University New Haven Connecticut 06520 USA Benjamin Levich Institute and Physics Department The City College of New York New York New York 10031 USA Department of Applied Physics Yale University New Haven Connecticut 06520 USA Graduate Program in Computational Biology and Bioinformatics Yale University New Haven Connecticut 06520 USA

We perform computational studies of static packings of a variety of nonspherical particles including circulo-lines, circulo-polygons, ellipses, asymmetric dimers, dumbbells, and others to determine which shapes form packings with fewer contacts than degrees of freedom (hypostatic packings) and which have equal numbers of contacts and degrees of freedom (isostatic packings), and to understand why hypostatic packings of nonspherical particles can be mechanically stable despite having fewer contacts than that predicted from naive constraint counting. To generate highly accurate force- and torque-balanced packings of circulo-lines and cir-polygons, we developed an interparticle potential that gives continuous forces and torques as a function of the particle coordinates. We show that the packing fraction and coordination number at jamming onset obey a masterlike form for all of the nonspherical particle packings we studied when plotted versus the particle asphericity A, which is proportional to the ratio of the squared perimeter to the area of the particle. Further, the eigenvalue spectra of the dynamical matrix for packings of different particle shapes collapse when plotted at the same A. For hypostatic packings of nonspherical particles, we verify that the number of “quartic” modes along which the potential energy increases as the fourth power of the perturbation amplitude matches the number of missing contacts relative to the isostatic value. We show that the fourth derivatives of the total potential energy in the directions of the quartic modes remain nonzero as the pressure of the packings is decreased to zero. In addition, we calculate the principal curvatures of the inequality constraints for each contact in circulo-line packings and identify specific types of contacts with inequality constraints that possess convex curvature. These contacts can constrain multiple degrees of freedom and allow hypostatic packings of nonspherical particles to be mechanically stable.

关键词： Granular materials Granular packing Jamming