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arXiv 2025年

作者： Ford, Nicole M. Nowak, Michael Ramakrishnan, Venkatessh Haggard, Daryl Dage, Kristen Nair, Dhanya G. Chan, Chi-Kwan Department of Physics McGill University 3600 Rue University MontrealQCH3A 2T8 Canada Trottier Space Institute 3550 Rue University MontréalQCH3A 2A7 Canada Department of Physics Washington University in Saint Louis MSC 1105-109-02 One Brookings Drive St. LouisMO63130-4899 United States Finnish Centre for Astronomy with ESO University of Turku TurkuFI-20014 Finland Aalto University Metsähovi Radio Observatory Metsähovintie 114 KylmäläFI-02540 Finland International Centre for Radio Astronomy Research Curtin University GPO Box U1987 PerthWA6845 Australia Astronomy Department Universidad de Concepción Casilla Concepción160-C Chile Max Planck Institute for Radio Astronomy Auf dem Hügel 69 Bonn53121 Germany Steward Observatory Department of Astronomy University of Arizona 933 N. Cherry Avenue TucsonAZ85721 United States Data Science Institute University of Arizona 1230 N. Cherry Avenue TucsonAZ85721 United States Program in Applied Mathematics University of Arizona 617 N. Santa Rita TucsonAZ85721 United States

We present a 5 month NICER X-ray monitoring campaign for two low-luminosity active galactic nuclei (LLAGNs)—NGC 4594 and IC 1459—with complementary Swift and NuSTAR observations. Utilizing an absorbed power-law and thermal source model combined with NICER’s SCORPEON background model, we demonstrate the effectiveness of joint source–background modeling for constraining emission from faint, background-dominated targets. Both sources are dominated by nuclear power-law emission with photon indices Γ ∼ 1.5–2, with NGC 4594 being slightly harder than IC 1459. The thermal contribution in both sources is fainter, but constant, with kT ∼ 0.5 keV (∼5 × 106 K). The power-law flux and Γ are strongly anticorrelated in both sources, as has been seen for other LLAGNs with radiatively inefficient accretion flows. NGC 4594 is the brighter source and exhibits significant aperiodic variability. Its variability timescale with an upper limit of 5–7 days indicates emission originating from ≾100 rg, at the scale of the inner accretion flow. A spectral break found at ∼6 keV, while tentative, could arise from synchrotron/inverse Compton emission. This high-cadence LLAGN X-ray monitoring campaign underlines the importance of multiwavelength variability studies for a sample of LLAGNs to truly understand their accretion and outflow physics. © 2025, CC BY.

关键词： Active Galactic Nuclei

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Building Three-Dimensional Differentiable Manifolds Numerically

arXiv

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arXiv 2021年

作者： Lindblom, Lee Rinne, Oliver Taylor, Nicholas W. Center for Astrophysics and Space Sciences University of California at San Diego 9500 Gilman Drive La JollaCA92093 United States Center for Computational Mathematics University of California at San Diego 9500 Gilman Drive La JollaCA92093 United States Faculty 4 HTW Berlin University of Applied Sciences Treskowallee 8 Berlin10318 Germany Department of Physics Cornell University IthacaNY14853 United States

A method is developed here for building differentiable three-dimensional manifolds on multicube structures. This method constructs a sequence of reference metrics that determine differentiable structures on the cubic regions that serve as non-overlapping coordinate charts on these manifolds. It uses solutions to the two- and three-dimensional biharmonic equations in a sequence of steps that increase the differentiability of the reference metrics across the interfaces between cubic regions. This method is algorithmic and has been implemented in a computer code that automatically generates these reference metrics. Examples of three-manifolds constructed in this way are presented here, including representatives from five of the eight Thurston geometrization classes, plus the well-known Hantzsche-Wendt, the Poincare dodecahedral space, and the Seifert-Weber space. Copyright © 2021, The Authors. All rights reserved.

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Multifunctional Resonant Wavefront-Shaping Meta-Optics Based on Multilayer and Multi-Perturbation Nonlocal Metasurfaces

arXiv

引用

arXiv 2020年

作者： Malek, Stephanie C. Overvig, Adam C. Alù, Andrea Yu, Nanfang Department of Applied Physics and Applied Mathematics Columbia University New YorkNY10027 United States Photonics Initiative Advanced Science Research Center City University of New York New YorkNY10031 United States Physics Program Graduate Center City University of New York New YorkNY10016 United States

Photonic devices rarely provide both elaborate spatial control and sharp spectral control over an incoming wavefront. In optical metasurfaces, for example, the localized modes of individual meta-units govern the wavefront shape over a broad bandwidth, while nonlocal lattice modes extended over many unit cells support high quality-factor resonances. Here, we experimentally demonstrate nonlocal dielectric metasurfaces in the near-infrared that offer both spatial and spectral control of light, realizing metalenses focusing light exclusively over a narrowband resonance while leaving off-resonant frequencies unaffected. Our devices attain this functionality by supporting a quasi-bound state in the continuum encoded with a spatially varying geometric phase. We leverage this capability to experimentally realize a versatile platform for multispectral wavefront shaping where a stack of metasurfaces, each supporting multiple independently controlled quasi-bound states in the continuum, molds the optical wavefront distinctively at multiple wavelengths and yet stay transparent over the rest of the spectrum. Such a platform is scalable to the visible for applications in augmented reality and transparent displays. Copyright © 2020, The Authors. All rights reserved.

关键词： Wavefronts

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Systematic study of flow vector fluctuations in sNN=5.02 TeV Pb-Pb collisions

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Physical Review C 2024年第6期109卷 065202-065202页

作者： S. Acharya D. Adamová A. Agarwal G. Aglieri Rinella L. Aglietta M. Agnello N. Agrawal Z. Ahammed S. Ahmad S. U. Ahn I. Ahuja A. Akindinov V. Akishina M. Al-Turany D. Aleksandrov B. Alessandro H. M. Alfanda R. Alfaro Molina B. Ali A. Alici N. Alizadehvandchali A. Alkin J. Alme G. Alocco T. Alt A. R. Altamura I. Altsybeev J. R. Alvarado M. N. Anaam C. Andrei N. Andreou A. Andronic E. Andronov V. Anguelov F. Antinori P. Antonioli N. Apadula L. Aphecetche H. Appelshäuser C. Arata S. Arcelli M. Aresti R. Arnaldi J. G. M. C. A. Arneiro I. C. Arsene M. Arslandok A. Augustinus R. Averbeck M. D. Azmi H. Baba A. Badalà J. Bae Y. W. Baek X. Bai R. Bailhache Y. Bailung R. Bala A. Balbino A. Baldisseri B. Balis D. Banerjee Z. Banoo V. Barbasova F. Barile L. Barioglio M. Barlou B. Barman G. G. Barnaföldi L. S. Barnby E. Barreau V. Barret L. Barreto C. Bartels K. Barth E. Bartsch N. Bastid S. Basu G. Batigne D. Battistini B. Batyunya D. Bauri J. L. Bazo Alba I. G. Bearden C. Beattie P. Becht D. Behera I. Belikov A. D. C. Bell Hechavarria F. Bellini R. Bellwied S. Belokurova L. G. E. Beltran Y. A. V. Beltran G. Bencedi A. Bensaoula S. Beole Y. Berdnikov A. Berdnikova L. Bergmann M. G. Besoiu L. Betev P. P. Bhaduri A. Bhasin M. A. Bhat B. Bhattacharjee L. Bianchi N. Bianchi J. Bielčík J. Bielčíková A. P. Bigot A. Bilandzic G. Biro S. Biswas N. Bize J. T. Blair D. Blau M. B. Blidaru N. Bluhme C. Blume G. Boca F. Bock T. Bodova J. Bok L. Boldizsár M. Bombara P. M. Bond G. Bonomi H. Borel A. Borissov A. G. Borquez Carcamo H. Bossi E. Botta Y. E. M. Bouziani L. Bratrud P. Braun-Munzinger M. Bregant M. Broz G. E. Bruno M. D. Buckland D. Budnikov H. Buesching S. Bufalino P. Buhler N. Burmasov Z. Buthelezi A. Bylinkin S. A. Bysiak J. C. Cabanillas Noris M. F. T. Cabrera M. Cai H. Caines A. Caliva E. Calvo Villar J. M. M. Camacho P. Camerini F. D. M. Canedo S. L. Cantway M. Carabas A. A. Carballo F. Carnesecchi R. Caron L. A. D. Carvalho J. Castillo Castellanos M. Castoldi F. Catalano S. Cattaruzzi C. Ceballos Sanchez R. Cerri I. Chakabe CNRS/IN2P3 LPC Clermont-Ferrand France Nuclear Physics Institute of the Czech Academy of Sciences Husinec-Řež Czech Republic Homi Bhabha National Institute Kolkata India Geneva Switzerland and Sezione INFN Turin Italy and Sezione INFN Bologna Italy Department of Physics Daejeon Republic of Korea Faculty of Science Affiliated with an institute covered by a cooperation agreement with CERN Frankfurt Institute for Advanced Studies Research Division and ExtreMe Matter Institute EMMI Turin Italy Wuhan China Instituto de Física Houston Texas USA Sungkyunkwan University Suwon City Republic of Korea Department of Physics and Technology Cagliari Italy Institut für Kernphysik Bari Italy Physik Department Technische Universität München Munich Germany High Energy Physics Group Bucharest Romania University of Derby Derby United Kingdom Institut für Kernphysik Münster Germany Physikalisches Institut Padova Italy Bologna Italy Berkeley California USA SUBATECH Université Grenoble-Alpes CNRS-IN2P3 Grenoble France and Sezione INFN Cagliari Italy São Paulo Brazil New Haven Connecticut USA Tokyo Japan Catania Italy Gangneung Republic of Korea Hefei China Indore India Physics Department Université Paris-Saclay Centre d'Etudes de Saclay (CEA) IRFU Départment de Physique Nucléaire (DPhN) Saclay France Cracow Poland Department of Physics and Centre for Astroparticle Physics and Space Science (CAPSS) Kolkata India and Sezione INFN Bari Italy School of Science Department of Physics Athens Greece Department of Physics Guwahati India Budapest Hungary Liverpool United Kingdom Department of Physics Division of Particle Physics Lund Sweden Affiliated with an international laboratory covered by a cooperation agreement with CERN Mumbai India Sección Física Departamento de Ciencias Niels Bohr Institute CNRS IPHC UMR 7178 F-67000 Strasbourg France Strasbourg France Universidad Autónoma de Sinaloa Culiacá

Measurements of the pT-dependent flow vector fluctuations in Pb–Pb collisions at sNN=5.02TeV using azimuthal correlations with the ALICE experiment at the Large Hadron Collider are presented. A four-particle correlation approach [ALICE Collaboration, Phys. Rev. C 107, L051901 (2023)] is used to quantify the effects of flow angle and magnitude fluctuations separately. This paper extends previous studies to additional centrality intervals and provides measurements of the pT-dependent flow vector fluctuations at sNN=5.02TeV with two-particle correlations. Significant pT-dependent fluctuations of the V⃗2 flow vector in Pb–Pb collisions are found across different centrality ranges, with the largest fluctuations of up to ∼15% being present in the 5% most central collisions. In parallel, no evidence of significant pT-dependent fluctuations of V⃗3 or V⃗4 is found. Additionally, evidence of flow angle and magnitude fluctuations is observed with more than 5σ significance in central collisions. These observations in Pb–Pb collisions indicate where the classical picture of hydrodynamic modeling with a common symmetry plane breaks down. This has implications for hard probes at high pT, which might be biased by pT-dependent flow angle fluctuations of at least 23% in central collisions. Given the presented results, existing theoretical models should be reexamined to improve our understanding of initial conditions, quark–gluon plasma properties, and the dynamic evolution of the created system.

关键词： Particle correlations & fluctuations Quark-gluon plasma Relativistic heavy-ion collisions

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Cryo-EM reconstruction of continuous heterogeneity by Laplacian spectral volumes

arXiv

引用

arXiv 2019年

作者： Moscovich, Amit Halevi, Amit Andén, Joakim Singer, Amit Program in Applied & Computational Mathematics Princeton University Princeton NJ United States Center for Computational Mathematics Flatiron Institute New YorkNY United States Department of Mathematics Princeton University Princeton NJ United States

Single-particle electron cryomicroscopy is an essential tool for high-resolution 3D reconstruction of proteins and other biological macromolecules. An important challenge in cryo-EM is the reconstruction of non-rigid molecules with parts that move and deform. Traditional reconstruction methods fail in these cases, resulting in smeared reconstructions of the moving parts. This poses a major obstacle for structural biologists, who need high-resolution reconstructions of entire macromolecules, moving parts included. To address this challenge, we present a new method for the reconstruction of macromolecules exhibiting continuous heterogeneity. The proposed method uses projection images from multiple viewing directions to construct a graph Laplacian through which the manifold of three-dimensional conformations is analyzed. The 3D molecular structures are then expanded in a basis of Laplacian eigenvectors, using a novel generalized tomographic reconstruction algorithm to compute the expansion coefficients. These coefficients, which we name spectral volumes, provide a high-resolution visualization of the molecular dynamics. We provide a theoretical analysis and evaluate the method empirically on several simulated data *** Codes 62P10, 65R32, 94A08 Copyright © 2019, The Authors. All rights reserved.

关键词： Macromolecules

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Topology and Kinetic Pathways of Colloidosome Assembly and Disassembly

arXiv

引用

arXiv 2025年

作者： Adkins, Raymond Robaszewski, Joanna Shin, Seungwoo Brauns, Fridtjof Jia, Leroy Khanra, Ayantika Sharma, Prerna Pelcovits, Robert Powers, Thomas R. Dogic, Zvonimir Department of Physics University of California Santa Barbara Santa BarbaraCA93106 United States Molecular Biophysics and Biochemistry Yale University New HavenCT06510 United States Environmental Laboratory US Army Engineer Research and Development Center ConcordMA01742 United States Kavli Institute for Theoretical Physics University of California Santa Barbara Santa BarbaraCA93106 United States Applied and Computational Mathematics Division National Institute of Standards and Technology GaithersburgMD20899 United States Department of Physics Indian Institute of Science Bangalore560012 India Department of Bioengineering Indian Institute of Science Bangalore560012 India Department of Physics Brown University ProvidenceRI02906 United States School of Engineering Brown University ProvidenceRI02906 United States

Liquid shells, such as lipid vesicles and soap bubbles, are ubiquitous throughout biology, engineered matter, and everyday life. Their creation and disintegration are defined by a singularity that separates a topologically distinct extended liquid film from a boundary-free closed shell. Such topology-changing processes are essential for cellular transport and drug delivery. However, their studies are challenging because of the rapid dynamics and small length scale of conventional lipid vesicles. We develop fluid colloidosomes, micron-sized analogs of lipid vesicles. We study their stability close to their disk-to-sphere topological transition. Intrinsic colloidal length and time scales slow down the dynamics to reveal vesicle conformations in real time during their assembly and disassembly. Remarkably, the lowest-energy pathway by which a closed vesicle transforms into a disk involves a topologically distinct cylinder-like intermediate. These results reveal universal aspects of topological changes in all liquid shells and a robust platform for the encapsulation, transport, and delivery of nanosized cargoes. © 2025, CC BY.

关键词： Controlled drug delivery

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Towards Cleaner Air: Pm2.5 Exposure and Disparities Around Childcare Providers in England

SSRN

引用

SSRN 2025年

作者： Cruz, Joana Li, Guangquan Rammah, Amal Zhong, Jian Shoari, Niloofar Akaraci, Selin Hajna, Samantha Hart, Caroline Chamberlain, Rosemary Mitsakou, Christina Exley, Karen Bloss, William Fry, Richard Cummins, Steven Hardelid, Pia Population Policy and Practice Research and Teaching Department Great Ormond Street Institute of Child Health UCL 30 Guilford Street LondonWC1N 1EH United Kingdom Applied Statistics Research Group Department of Mathematics Physics and Electrical Engineering Northumbria University Newcastle upon TyneNE1 8ST United Kingdom School of Geography Earth & Environmental Sciences University of Birmingham Edgbaston BirminghamB15 2TT United Kingdom Computational Science and Engineering Group University of Greenwich Old Royal Naval College Park Row LondonSE10 9LS United Kingdom Department of Health Sciences Faculty of Applied Health Sciences Brock University St Catharines ON Canada Air Quality and Public Health Environmental Hazards and Emergencies UK Health Security Agency ChiltonOX11 0RQ United Kingdom Swansea University Singleton Park Swansea WalesSA28PP United Kingdom Population Health Innovation Lab Department of Public Health Environments & Society London School of Hygiene & Tropical Medicine 15-17 Tavistock Place LondonWC1H 9SH United Kingdom GOSH Biomedical Research Centre 30 Guilford St LondonWC1N 1EH United Kingdom

Air pollution poses a significant health risk for young children, particularly in urbanareas. This study examined changes in PM2.5 concentrations around Early YearsProviders (EYPs)—including nurseries—across England from 2018 to 2022 andidentified neighbourhood characteristics associated with EYPs located in areasexceeding WHO air quality guidelines (>5 μg/m3). Geographic Information Systems(GIS) methodology integrated data on EYP locations from Ordnance Survey with airpollution data from *** analysed temporal changes in PM2.5 concentrations around EYPs, identifiedclusters exceeding WHO interim target levels of 10 μg/m3 using Local Moran’s I, andexplored associations between PM2.5 exposure and socio-demographic factors. Dataon deprivation, urbanicity, and ethnic group distribution were sourced from the 2021Census of Population for England and Wales. A Bayesian spatial regression modelincorporating random effects assessed associations between PM2.5 exposure andsmall-area socio-demographic *** 2018 and 2022, the number of EYPs ranged from 15,780 to 18,427. AveragePM2.5 levels around EYPs declined by 17.8% (from 9.4 μg/m3, SD=1.8 to 7.8 μg/m3,SD=1.5), yet over 96% of EYPs consistently recorded concentrations above the WHOannual guideline of 5 μg/m3. Temporary reductions during COVID-19 lockdowns in2020 (mean=7.5 μg/m3, SD=1.3) rebounded by ***-High clusters (EYPs with PM2.5 >10 μg/m3 surrounded by similar EYPs) wereobserved in urban centres like Greater London, Birmingham, and Southeast England,while Low-Low clusters occurred in rural regions such as Devon, Cornwall, and northern England. EYPs in deprived, urban areas with predominantly non-whitepopulations had higher PM2.5 *** findings highlight the urgent need for targeted interventions to reduce airpollution in deprived urban areas, prioritizing young children’s health. © 2025, The Authors. All rights reserved.

关键词： Health risks

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The barron space and the flow-induced function spaces for neural network models

arXiv

引用

arXiv 2019年

作者： Weinan, E. Ma, Chao Wu, Lei Department of Mathematics Princeton University United States Program in Applied and Computational Mathematics Princeton University United States Beijing Institute of Big Data Research China

One of the key issues in the analysis of machine learning models is to identify the appropriate function space and norm for the model. This is the set of functions endowed with a quantity which can control the approximation and estimation errors by a particular machine learning model. In this paper, we address this issue for two representative neural network models: The two-layer networks and the residual neural networks. We define the Barron space and show that it is the right space for two-layer neural network models in the sense that optimal direct and inverse approximation theorems hold for functions in the Barron space. For residual neural network models, we construct the so-called flow-induced function space, and prove direct and inverse approximation theorems for this space. In addition, we show that the Rademacher complexity for bounded sets under these norms has the optimal upper bounds. Copyright © 2019, The Authors. All rights reserved.

关键词： Functional analysis

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Pseudo mesh for adjoint weight flux in predictor corrector quasi static kinetics calculation in monte carlo code RMC

Pseudo mesh for adjoint weight flux in predictor corrector q...

引用

2018 International Conference on physics of Reactors: Reactor physics Paving the Way Towards More Efficient Systems, PHYSOR 2018

作者： Shang, Xiaotong Xu, Qi Wang, Kan Department of Engineering Physics Tsinghua University Beijing 100084 China Institute of Applied Physics and Computational Mathematics Beijing100084 China

ISBN: (纸本)9781713808510

The continuous energy Monte Carlo (MC) method for arbitrary geometry is playing a more and more important role in reactor physics analysis including both static (criticality and burnup) and transient calculations with the development of high performance computing (HPC) platform. Considering the high calculation time cost of the direct simulation method, predictor-corrector quasi-static (PCQS) method has been implemented in Monte Carlo Code RMC. In PCQS method, the neutron angular flux is factorized into the amplitude function and shape function. The calculation procedure consists of transient fixed source MC calculation in each macro time step which calculates the power distribution and estimates the point-kinetics parameters and the point-kinetics calculation in each micro time step. In this work, the transient fixed source MC calculation is solved by the modified fission source iteration method and a kind of pseudo mesh for the adjoint weight flux is proposed for the estimation of point-kinetics parameters. Rather than multi-group adjoint flux calculation, the adjoint weight flux in each mesh can be obtained from the Iterated fission probability (IFP) method implemented in RMC before which is suitable for continuous energy Monte Carlo eigenvalue calculation scheme. Then the point-kinetics equation is solved with the fourth order Runge-Kutta method. For code verification, the two-dimensional TWIGL problem is calculated and compared with the results of deterministic code MPACT, which shows a good agreement. © 2018 International Conference on physics of Reactors, PHYSOR 2018: Reactor physics Paving the Way Towards More Efficient Systems. All rights reserved.

关键词： Monte Carlo methods

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A spacetime finite elements method to solve the dirac equation

arXiv

引用

arXiv 2021年

作者： Sundermann, Rylee Lim, Hyun Waybright, Jace Kimn, Jung-Han Department of Mathematics and Statistics South Dakota State University BrookingsSD57007 United States Computational Physics and Methods Group Los Alamos National Laboratory Los AlamosNM87545 United States Center for Theoretical Astrophysics Los Alamos National Laboratory Los AlamosNM87545 United States Applied Computer Science Group Los Alamos National Laboratory Los AlamosNM87545 United States Princeton Plasma Physics Laboratory Princeton University PrincetonNJ08543 United States

In this work, a fully implicit numerical approach based on space-time finite element method is presented to solve the Dirac equation in 1 (space) + 1 (time), 2 + 1, and 3 + 1 dimensions. We utilize PETSc/Tao library to implement our linear system and for using Krylov subspace based solvers such as GMRES. We demonstrate our method by analyzing several different cases including plane wave solution, Zitterbewegung, and Klein paradox. Parallel performance of this implementation is also presented. © 2021, CC BY.

关键词： Finite element method

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