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The atacama cosmology telescope: DR5 maps of 18000 square degrees of the microwave sky from ACT 2008-2018 data

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arXiv 2020年

作者： Naess, Sigurd Aiola, Simone Austermann, Jason E. Battaglia, Nick Beall, James A. Becker, Daniel T. Bond, Richard J. Calabrese, Erminia Choi, Steve K. Cothard, Nicholas F. Crowley, Kevin T. Darwish, Omar Datta, Rahul Denison, Edward V. Devlin, Mark Duell, Cody J. Duff, Shannon M. Duivenvoorden, Adriaan J. Dunkley, Jo Dünner, Rolando Fox, Anna E. Gallardo, Patricio A. Halpern, Mark Han, Dongwon Hasselfield, Matthew Hill, J. Colin Hilton, Gene C. Hilton, Matt Hincks, Adam D. Hložek, Renée Ho, Shuay-Pwu Patty Hubmayr, Johannes Huffenberger, Kevin Hughes, John P. Kosowsky, Arthur B. Louis, Thibaut Madhavacheril, Mathew S. McMahon, Jeff Moodley, Kavilan Nati, Federico Nibarger, John P. Niemack, Michael D. Page, Lyman Partridge, Bruce Salatino, Maria Schaan, Emmanuel Schillaci, Alessandro Schmitt, Benjamin Sherwin, Blake D. Sehgal, Neelima Sifón, Cristóbal Spergel, David Staggs, Suzanne Stevens, Jason Storer, Emilie Ullom, Joel N. Vale, Leila R. van Engelen, Alexander van Lanen, Jeff Vavagiakis, Eve M. Wollack, Edward J. Xu, Zhilei Center for Computational Astrophysics Flatiron Institute New YorkNY10010 United States Department of Astrophysical Sciences Peyton Hall Princeton University PrincetonNJ08544 United States Joseph Henry Laboratories of Physics Jadwin Hall Princeton University PrincetonNJ08544 United States Department of Physics and Astronomy Haverford College HaverfordPA19041 United States Laboratoire de l’Accélérateur Linéaire Univ. Paris-Sud CNRS/IN2P3 Université Paris-Saclay Orsay France NASA/Goddard Space Flight Center GreenbeltMD20771 United States Physics and Astronomy Department Stony Brook University Stony BrookNY11794 United States Astrophysics Research Centre University of KwaZulu-Natal Westville Campus Durban4041 South Africa Department of Physics California Institute of Technology PasadenaCA91125 United States Instituto de Física Pontificia Universidad Católica de Valparaíso Chile Lawrence Berkeley National Laboratory BerkeleyCA94720 United States Berkeley Center for Cosmological Physics University of California BerkeleyCA94720 United States School of Physics and Astronomy Cardiff University The Parade Cardiff WalesCF24 3AA United Kingdom Department of Physics University of Milano-Bicocca Piazza della Scienza 3 MilanoMI20126 Italy Astrophysics Research Centre School of Mathematics Statistics and Computer Science University of KwaZulu-Natal Durban4041 South Africa Department of Physics and Astronomy Rutgers State University of New Jersey PiscatawayNJ08854-8019 United States StanfordCA United States Instituto de Astrofísica and Centro de Astro-Ingeniería Facultad de Física Pontificia Universidad Católica de Chile Av. Vicuña Mackenna 4860 Macul Santiago7820436 Chile Department of Physics Cornell University IthacaNY14853 United States Department of Astronomy Cornell University IthacaNY14853 United States Dept. of Physics and Astronomy Johns Hopkins University 3400 N. Charles St. BaltimoreMD21218 United States NIST Q

This paper presents a maximum-likelihood algorithm for combining sky maps with disparate sky coverage, angular resolution and spatially varying anisotropic noise into a single map of the sky. We use this to merge hundreds of individual maps covering the 2008–2018 ACT observing seasons, resulting in by far the deepest ACT maps released so far. We also combine the maps with the full Planck maps, resulting in maps that have the best features of both Planck and ACT: Planck’s nearly white noise on intermediate and large angular scales and ACT’s high-resolution and sensitivity on small angular scales. The maps cover over 18 000 square degrees, nearly half the full sky, at 100, 150 and 220 GHz. They reveal 4 000 optically-confirmed clusters through the Sunyaev Zel’dovich effect (SZ) and 18 500 point source candidates at > 5σ, the largest single collection of SZ clusters and millimeter wave sources to date. The multi-frequency maps provide millimeter images of nearby galaxies and individual Milky Way nebulae, and even clear detections of several nearby stars. Other anticipated uses of these maps include, for example, thermal SZ and kinematic SZ cluster stacking, CMB cluster lensing and galactic dust science. The method itself has negligible bias. However, due to the preliminary nature of some of the component data sets, we caution that these maps should not be used for precision cosmological analysis. The maps are part of ACT DR5, and are available on LAMBDA at https://***/product/act/actpol_prod_***. There is also a web atlas at https://***/public/snaess/actpol/dr5/atlas. © 2020, CC0.

关键词： Galaxies

Variational joint filtering

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arXiv 2017年

作者： Zhao, Yuan Park, Il Memming Department of Neurobiology and Behavior Stony Brook University Stony BrookNY11794 United States Department of Neurobiology and Behavior Department of Applied Mathematics and Statistics Institute for Advanced Computational Science Stony Brook University Stony BrookNY11794 United States

State space models provide an interpretable framework for complex time series by combining an intuitive dynamical system model with a probabilistic observation model. We developed a flexible online learning framework for latent nonlinear state dynamics and filtered latent states. Our method utilizes the stochastic gradient variational Bayes method to jointly optimize the parameters of the nonlinear dynamics, observation model, and the black-box recognition model. Unlike previous approaches, our framework can incorporate non-trivial observation noise models and has potential of inferring in real-time. We test our method on point process and Gaussian observations driven by continuous attractor dynamics and nonstationary systems, demonstrating its ability to recover the phase portrait, filtered trajectory, and produce long-term predictions for online machine learning. Copyright © 2017, The Authors. All rights reserved.

关键词： State space methods

A stochastic generator of global monthly wind energy with tukey g-and-h autoregressive processes

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arXiv 2017年

作者： Jeong, Jaehong Yan, Yuan Castruccio, Stefano Genton, Marc G. CEMSE Division King Abdullah University of Science and Technology Thuwal23955-6900 Saudi Arabia Department of Applied and Computational Mathematics and Statistics University of Notre Dame 153 Hurley Hall Notre DameIN46556 United States

Quantifying the uncertainty of wind energy potential from climate models is a very timeconsuming task and requires a considerable amount of computational resources. A statistical model trained on a small set of runs can act as a stochastic approximation of the original climate model, and be used to assess the uncertainty considerably faster than by resorting to the original climate model for additional runs. While Gaussian models have been widely employed as means to approximate climate simulations, the Gaussianity assumption is not suitable for winds at policy-relevant time scales, i.e., sub-annual. We propose a trans-Gaussian model for monthly wind speed that relies on an autoregressive structure with Tukey g-and-h transformation, a exible new class that can separately model skewness and tail behavior. This temporal structure is integrated into a multi-step spectral framework that is able to account for global nonstationarities across land/ocean boundaries, as well as across mountain ranges. Inference can be achieved by balancing memory storage and distributed computation for a data set of 220 million points. Once fitted with as few as five runs, the statistical model can generate surrogates fast and efficiently on a simple laptop, and provide uncertainty assessments very close to those obtained from all the available climate simulations (forty) on a monthly scale. Copyright © 2017, The Authors. All rights reserved.

关键词： Stochastic systems

Simulating spin dynamics with spin-dependent cross sections in heavy-ion collisions

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Physical Review C 2017年第4期96卷 044618-044618页

作者： Yin Xia Jun Xu Bao-An Li Wen-Qing Shen Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201800 China University of Chinese Academy of Sciences Beijing 100049 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China Department of Physics and Astronomy Texas A&M University-Commerce Commerce Texas 75429-3011 USA Department of Applied Physics Xi'an Jiao Tong University Xi'an 710049 China

We have incorporated the spin-dependent nucleon-nucleon cross sections into a Boltzmann-Uehling-Uhlenbeck transport model for the first time, using the spin-singlet and spin-triplet nucleon-nucleon elastic scattering cross sections extracted from the phase-shift analyses of nucleon-nucleon scatterings in free space. We found that the spin splitting of the collective flows is not affected by the spin-dependent cross sections, justifying it as a good probe of the in-medium nuclear spin-orbit interaction. With the in-medium nuclear spin-orbit mean-field potential that leads to local spin polarization, we found that the spin-averaged observables, such as elliptic flows of free nucleons and light clusters, becomes smaller with the spin-dependent differential nucleon-nucleon scattering cross sections.

关键词： Low & intermediate energy heavy-ion reactions Nuclear spin & parity Nucleon-nucleon interactions Polarization phenomena Hydrodynamic models

A fluctuating boundary integral method for brownian suspensions

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arXiv 2017年

作者： Bao, Yuanxun Rachh, Manas Keaveny, Eric E. Greengard, Leslie Donev, Aleksandar Courant Institute of Mathematical Sciences New York University 251 Mercer Street New YorkNY United States Applied Mathematics Program Yale University New HavenCT06511 United States Department of Mathematics Imperial College London LondonSW7 2AZ United Kingdom Center for Computational Biology Flatiron Institute New YorkNY United States

We present a fluctuating boundary integral method (FBIM) for overdamped Brownian Dynamics (BD) of two-dimensional periodic suspensions of rigid particles of complex shape immersed in a Stokes fluid. We develop a novel approach for generating Brownian displacements that arise in response to the thermal fluctuations in the fluid. Our approach relies on a first-kind boundary integral formulation of a mobility problem in which a random surface velocity is prescribed on the particle surface, with zero mean and covariance proportional to the Green’s function for Stokes flow (Stokeslet). This approach yields an algorithm that scales linearly in the number of particles for both deterministic and stochastic dynamics, handles particles of complex shape, achieves high order of accuracy, and can be generalized to three dimensions and other boundary conditions. We show that Brownian displacements generated by our method obey the discrete fluctuation-dissipation balance relation (DFDB). Based on a recently-developed Positively Split Ewald method [A. M. Fiore, F. Balboa Usabiaga, A. Donev and J. W. Swan, J. Chem. Phys., 146, 124116, 2017], near-field contributions to the Brownian displacements are efficiently approximated by iterative methods in real space, while far-field contributions are rapidly generated by fast Fourier-space methods based on fluctuating hydrodynamics. FBIM provides the key ingredient for time integration of the overdamped Langevin equations for Brownian suspensions of rigid particles. We demonstrate that FBIM obeys DFDB by performing equilibrium BD simulations of suspensions of starfish-shaped bodies using a random finite difference temporal integrator. Copyright © 2017, The Authors. All rights reserved.

关键词： Boundary integral equations

Smart Innovation, Systems and Technologies

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Preface

Smart Innovation, Systems and Technologies 2019年 133卷 v页

作者： Petrov, Igor B. Favorskaya, Alena V. Favorskaya, Margarita N. Simakov, Sergey S. Jain, Lakhmi C. Department of Computer Science and Numerical Mathematics Moscow Institute of Physics and Technology The Moscow Area Dolgoprudny Russia Department of Applied Computational Geophysics Moscow Institute of Physics and Technology The Moscow Area Dolgoprudny Russia Institute of Informatics and Telecommunications Reshetnev Siberian State University of Science and Technology Krasnoyarsk Russia Department of Computational Physics Moscow Institute of Physics and Technology The Moscow Area Dolgoprudny Russia Faculty of Engineering and Information Technology Centre for Artificial Intelligence University of Technology SydneyNSW Australia Faculty of Science and Technology University of Canberra CanberraACT Australia Faculty of Science Liverpool Hope University Liverpool United Kingdom KES International Shoreham-by-Sea United Kingdom

Inertial Hegselmann-Krause systems

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Inertial Hegselmann-Krause systems

American Control Conference (ACC)

作者： Bernard Chazelle Chu Wang Department of Computer Science Princeton University Program in Applied and Computational Mathematics Princeton University

ISBN: (纸本)9781467386838

We derive an energy bound for inertial Hegselmann-Krause (HK) systems, which we define as a variant of the classic HK model in which the agents can change their weights arbitrarily at each step. We use the bound to prove the convergence of HK systems with closed-minded agents, which settles a conjecture of long standing. This paper also introduces anchored HK systems and show their equivalence to the symmetric heterogeneous model.

关键词： Convergence Communication networks Kinetic theory Protocols Nickel Mobile communication Turning

Random scalar fields and hyperuniformity

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arXiv 2017年

作者： Ma, Zheng Torquato, Salvatore Department of Physics Princeton University PrincetonNJ08544 United States Department of Chemistry Princeton University PrincetonNJ08544 United States Princeton Institute for the Science and Technology of Materials Princeton University PrincetonNJ08544 United States Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States

Disordered many-particle hyperuniform systems are exotic amorphous states of matter that lie between crystals and liquids. Hyperuniform systems have attracted recent attention because they are endowed with novel transport and optical properties. Recently, the hyperuniformity concept has been generalized to characterize two-phase media, scalar fields and random vector fields. In this paper, we devise methods to explicitly construct hyperuniform scalar fields. Specifically, we analyze spatial patterns generated from Gaussian random fields, which have been used to model the microwave background radiation and heterogeneous materials, the Cahn-Hilliard equation for spinodal decomposition, and Swift-Hohenberg equations that have been used to model emergent pattern formation, including Rayleigh-Bénard convection. We show that the Gaussian random scalar fields can be constructed to be hyperuniform. We also numerically study the time evolution of spinodal decomposition patterns and demonstrate that they are hyperuniform in the scaling regime. Moreover, we find that labyrinth-like patterns generated by the Swift-Hohenberg equation are effectively hyperuniform. We show that thresholding (level-cutting) a hyperuniform Gaussian random field to produce a two-phase random medium tends to destroy the hyperuniformity of the progenitor scalar field. We then propose guidelines to achieve effectively hyperuniform two-phase media derived from thresholded non-Gaussian fields. Our investigation paves the way for new research directions to characterize the large-structure spatial patterns that arise in physics, chemistry, biology and ecology. Moreover, our theoretical results are expected to guide experimentalists to synthesize new classes of hyperuniform materials with novel physical properties via coarsening processes and using state-of-the-art techniques, such as stereolithography and 3D printing. Copyright © 2017, The Authors. All rights reserved.

关键词： Gaussian distribution

Designing disordered hyperuniform two-phase materials with novel physical properties

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arXiv 2017年

作者： Chen, D. Torquato, S. Department of Chemistry Princeton University PrincetonNJ08544 United States Department of Physics Princeton University PrincetonNJ08544 United States Princeton Institute for the Science and Technology of Materials Princeton University PrincetonNJ08544 United States Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States

Heterogeneous materials consisting of different phases are ideally suited to achieve a broad spectrum of desirable bulk physical properties by combining the best features of the constituents through the strategic spatial arrangement of the different phases. Disordered hyperuniform heterogeneous materials are new, exotic amorphous matter that behave like crystals in the manner in which they suppress volume-fraction fluctuations at large length scales, and yet are isotropic with no Bragg peaks. In this paper, we formulate for the first time a Fourier-space numerical construction procedure to design at will a wide class of disordered hyperuniform two-phase materials with prescribed spectral densities, which enables one to tune the degree and length scales at which this suppression occurs. We demonstrate that the anomalous suppression of volume-fraction fluctuations in such two-phase materials endow them with novel and often optimal transport and electromagnetic properties. Specifically, we construct a family of phase-inversion-symmetric materials with variable topological connectedness properties that remarkably achieves a well-known explicit formula for the effective electrical (thermal) conductivity. Moreover, we design disordered stealthy hyperuniform dispersion that possesses nearly optimal effective conductivity while being statistically isotropic. Interestingly, all of our designed materials are transparent to electromagnetic radiation for certain wavelengths, which is a common attribute of all hyperuniform materials. Our constructed materials can be readily realized by 3D printing and lithographic technologies. We expect that our designs will be potentially useful for energy-saving materials, batteries and aerospace applications. Copyright © 2017, The Authors. All rights reserved.

关键词： Volume fraction