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Laser ring structures in step-index fibers

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Laser ring structures in step-index fibers

International Conference on Electronics, Engineering physics and Earth science 2022, EEPES 2022

作者： Slavchev, V. Dakova, A. Gocheva, N. Bozhikoliev, I. Kovachev, K. Biswas, A. Nonlinear and Fiber Optics Institute of Electronics Bulgarian Academy of Science 72 Tzarigradcko shossee Sofia1784 Bulgaria Physics and Technology Faculty University of Plovdiv "paisii Hilendarski 24 Tsar Asen Str. Plovdiv4000 Bulgaria Department of Medical Physics and Biophysics Medical University-Plovdiv 15 Vasil Aprilov Bul. Plovdiv4002 Bulgaria Department of Applied Mathematics National Research Nuclear University 31 Kashirskoe Hwy Moscow115409 Russia Research Group Department of Mathematics King Abdulaziz University Jeddah21589 Saudi Arabia Department of Mathematics and Applied Mathematics Sefako Makgatho Health Sciences University Medunsa Pretoria0204 South Africa Department of Physics Chemistry and Mathematics Alabama Agricultural and Mechanical University NormalAL35762-4900 United States Department of Applied Sciences Cross-Border Faculty Dunarea de Jos University of Galati 111 Domneasca Street Galati800201 Romania

The formation and propagation of optical ring structures, given by a system of amplitude equations for the components of the electric field is investigated. The calculations are made in approximation of second-order linear dispersion and self-phase modulation. New class analytical solutions, characterizing the generation and evolution of laser ring structures in optical waveguides with step-index profile and anomalous dispersion, are described in the present work. The stability of these optical formations is a result of the specific combination of nonlinearity, diffraction and angular distribution. Laser vortices have an amplitude type of singularity which appears as depolarization of the vector field in the light radiation spot. © 2022 Published under licence by IOP Publishing Ltd.

关键词： Dispersion (waves)

VERTEX-REMOVAL STABILITY AND THE LEAST POSITIVE VALUE OF HARMONIC MEASURES

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arXiv 2023年

作者： Cai, Zhenhao Kozma, Gady Procaccia, Eviatar B. Zhang, Yuan School of Mathematical Sciences Peking University Beijing China Faculty of Mathematics and Computer Science Weizmann Institute of Science Rehovot Israel Faculty of Data and Decision Sciences Technion Israel Institute of Technology Haifa Israel Center for Applied Statistics School of Statistics Renmin University of China Beijing China

We prove that for $\\mathbb{Z}^d$ ($d\\ge 2$), the vertex-removal stability ofharmonic measures (i.e. it is feasible to remove some vertex while changing theharmonic measure by a bounded factor) holds if and only if $d=2$. The proofmainly relies on geometric arguments, with a surprising use of the discreteKlein bottle. Moreover, a direct application of this stability verifies aconjecture of Calvert, Ganguly and Hammond [9] for the exponential decay of theleast positive value of harmonic measures on $\\mathbb{Z}^2$. Furthermore, theanalogue of this conjecture for $\\mathbb{Z}^d$ with $d\\ge 3$ is also proved inthis paper, despite vertex-removal stability no longer holding. © 2023, CC BY.

关键词： Bottles

SURVIVAL OF THE FITTEST: TESTING SUPERRADIANCE TERMINATION WITH SIMULATED BINARY BLACK HOLE STATISTICS

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arXiv 2024年

作者： Zhu, Hui-Yu Tong, Xi Manzoni, Giorgio Ma, Yanjiao Department of Physics The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong Jockey Club Institute for Advanced Study The Hong Kong University of Science and Technology Hong Kong Department of Applied Mathematics and Theoretical Physics University of Cambridge Wilberforce Road CambridgeCB3 0WA United Kingdom

The superradiance instability of rotating black holes leads to the formation of an ultralight boson cloud with distinctive observational signatures, making black holes an effective probe of ultralight dark matter. However, around black holes in a binary system, the superradiance effect of such clouds can be terminated by tidal perturbations from the companion, leading to cloud depletion. In this study, we perform the first analysis of the impact of this termination effect on superradiant black hole binaries which are realistically modelled after their statistics in our Galaxy. Working with a dataset of approximately 107 black hole binaries simulated using the Stellar EVolution for N-body (SEVN) population synthesis code, we identify the superradiant candidates and those that manage to survive the termination effect. We then calculate the cloud survival rate for various boson masses and black hole spin models. Our findings reveal that the l = m = 1 cloud modes are generally stable against termination, whereas the l = m = 2 modes can be significantly affected, with survival rates dropping below 10% for boson masses below approximately 0.5 × 10−12 eV. In addition, our analysis indicates that clouds that overcome termination typically exhibit a higher superradiant growth rate and therefore a higher detectability. © 2024, CC BY.

关键词： Bosons

Provably Convergent Plug-and-Play Quasi-Newton Methods

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arXiv 2023年

作者： Tan, Hong Ye Mukherjee, Subhadip Tang, Junqi Schönlieb, Carola-Bibiane Department of Applied Mathematics and Theoretical Physics University of Cambridge United Kingdom Department of Computer Science University of Bath United Kingdom School of Mathematics University of Birmingham United Kingdom Department of Electronics and Electrical Communication Engineering Indian Institute of Technology Kharagpur India

Plug-and-Play (PnP) methods are a class of efficient iterative methods that aim to combine data fidelity terms and deep denoisers using classical optimization algorithms, such as ISTA or ADMM, with applications in inverse problems and imaging. Provable PnP methods are a subclass of PnP methods with convergence guarantees, such as fixed point convergence or convergence to critical points of some energy function. Many existing provable PnP methods impose heavy restrictions on the denoiser or fidelity function, such as nonexpansiveness or strict convexity, respectively. In this work, we propose a novel algorithmic approach incorporating quasi-Newton steps into a provable PnP framework based on proximal denoisers, resulting in greatly accelerated convergence while retaining light assumptions on the denoiser. By characterizing the denoiser as the proximal operator of a weakly convex function, we show that the fixed points of the proposed quasi-Newton PnP algorithm are critical points of a weakly convex function. Numerical experiments on image deblurring and super-resolution demonstrate 2-8x faster convergence as compared to other provable PnP methods with similar reconstruction *** Codes 49M15, 49J52, 65K15 Copyright © 2023, The Authors. All rights reserved.

关键词： Image reconstruction

Application of HPC and big data in post-pandemic times

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Earthquake Research Advances 2021年第3期1卷 21-28页

作者： Henry M.Tufo David A.Yuen Gabriele Morra Matthew G.Knepley Bei Zhang Shi Chen Dept.of Computer Science University of ColoradoBoulderUSA Dept.of Applied Physics and Applied Mathematics Columbia UniversityUSA College of Information Science and Engineering and College of Marine Geosciences Ocean University of ChinaQingdaoChina Dept.of Physics and Earth Sciences University of LouisianaLafayetteLouisianaUSA Dept.of Computer Science and Engineering State University of New YorkBuffaloUSA Institute of Geophysics China Earthquake AdministrationBeijingChina Beijing Baijiatuan Earth Science National Observation and Research StationBeijingChina

We lay out the ramifications of the 2020 pandemic for all people in geosciences,especially the young,and argue for significant changes on training and career *** focus primarily on its devastating impact in USA and compare with that in other countries especially *** review the potential effect for the next four years or so on the aspirations of an academic career versus more realistic career *** urge people in mid-career about the need to reassess previous *** stress the need for students or researchers to acquire technical skills in high-performance computing(HPC),data analytics,artificial intelligence,and/or visualization along with a broad set of technical skills in applied computer science and *** give advice about hot prospects in several areas that have great potential for advancement in the coming decade,such as visualization,deep learning,quantum computing and information,and cloud computing,all of which lie within the aegis of *** forecast is that the pandemic will significantly reshape the job landscape and career paths for both young and established researchers and we discuss bluntly the dire situation facing junior people in geosciences in the aftermath of the pandemic around the world until 2024.

关键词： Geophysics High-performance computing Higher education Post-pandemic era

Imaging atomic-scale chemistry from fused multi-modal electron microscopy

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npj Computational Materials 2022年第1期8卷 164-171页

作者： Jonathan Schwartz Zichao Wendy Di Yi Jiang Alyssa J.Fielitz Don-Hyung Ha Sanjaya D.Perera Ismail El Baggari Richard D.Robinson Jeffrey A.Fessler Colin Ophus Steve Rozeveld Robert Hovden Department of Materials Science and Engineering University of MichiganAnn ArborMIUSA Mathematics and Computer Science Division Argonne National LaboratoryLemontILUSA Advanced Photon Source Facility Argonne National LaboratoryLemontILUSA Dow Chemical Co. MidlandMIUSA Department of Material Science and Engineering Cornell UniversityIthacaNew YorkUSA School of Integrative Engineering Chung-Ang UniversitySeoulRepublic of Korea Department of Physics Cornell UniversityIthacaNYUSA The Rowland Institute at Harvard CambridgeMAUSA Department of Electrical Engineering and Computer Science University of MichiganAnn ArborMIUSA National Center for Electron Microscopy Lawrence Berkeley National LaboratoryMolecular FoundryBerkeleyCAUSA Applied Physics Program University of MIchiganAnn ArborMIUnited States

Efforts to map atomic-scale chemistry at low doses with minimal noise using electron microscopes are fundamentally limited by inelastic ***,fused multi-modal electron microscopy offers high signal-to-noise ratio(SNR)recovery of material chemistry at nano-and atomic-resolution by coupling correlated information encoded within both elastic scattering(high-angle annular dark-field(HAADF))and inelastic spectroscopic signals(electron energy loss(EELS)or energy-dispersive x-ray(EDX)).By linking these simultaneously acquired signals,or modalities,the chemical distribution within nanomaterials can be imaged at significantly lower doses with existing detector *** many cases,the dose requirements can be reduced by over one order of *** high SNR recovery of chemistry is tested against simulated and experimental atomic resolution data of heterogeneous nanomaterials.

关键词： materials chemistry fused

The OpenLAM Challenges

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arXiv 2025年

作者： Peng, Anyang Liu, Xinzijian Guo, Ming-Yu Zhang, Linfeng Wang, Han AI for Science Institute Beijing100080 China DP Technology Beijing100080 China HEDPS CAPT College of Engineering Peking University Beijing100871 China Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Fenghao East Road 2 Beijing100094 China School of Chemistry Sun Yat-sen University Guangzhou510006 China

Inspired by the success of Large Language Models (LLMs), the development of Large Atom Models (LAMs) has gained significant momentum in scientific computation. Since 2022, the Deep Potential team has been actively pretraining LAMs and launched the OpenLAM Initiative to develop an open-source foundation model spanning the periodic table. A core objective is establishing comprehensive benchmarks for reliable LAM evaluation, addressing limitations in existing datasets. As a first step, the LAM Crystal Philately competition has collected over 19.8 million valid structures, including 1 million on the OpenLAM convex hull, driving advancements in generative modeling and materials science applications. Copyright © 2025, The Authors. All rights reserved.

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Hamiltonian bridge: A physics-driven generative framework for targeted pattern control

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arXiv 2024年

作者： Krishnan, Vishaal Sinha, Sumit Mahadevan, L. School of Engineering and Applied Sciences Harvard University CambridgeMA02138 United States Department of Data Science Dana-Farber Cancer Institute BostonMA United States Departments of Physics and Organismic and Evolutionary Biology Harvard University CambridgeMA02138 United States

Patterns arise spontaneously in a range of systems spanning the sciences, and their study typically focuses on mechanisms to understand their evolution in space-time. Increasingly, there has been a transition towards controlling these patterns in various functional settings, with implications for engineering. Here, we combine our knowledge of a general class of dynamical laws for pattern formation in non-equilibrium systems, and the power of stochastic optimal control approaches to present a framework that allows us to control patterns at multiple scales, which we dub the "Hamiltonian bridge". We use a mapping between stochastic many-body Lagrangian physics and deterministic Eulerian pattern forming PDEs to leverage our recent approach utilizing the Feynman-Kac-based adjoint path integral formulation for the control of interacting particles and generalize this to the active control of patterning fields. We demonstrate the applicability of our computational framework via numerical experiments on the control of phase separation with and without a conserved order parameter, self-assembly of fluid droplets, coupled reaction-diffusion equations and finally a phenomenological model for spatio-temporal tissue differentiation. We interpret our numerical experiments in terms of a theoretical understanding of how the underlying physics shapes the geometry of the pattern manifold, altering the transport paths of patterns and the nature of pattern interpolation. We finally conclude by showing how optimal control can be utilized to generate complex patterns via an iterative control protocol over pattern forming pdes which can be casted as gradient flows. All together, our study shows how we can systematically build in physical priors into a generative framework for pattern control in non-equilibrium systems across multiple length and time scales. Copyright © 2024, The Authors. All rights reserved.

关键词： Stochastic systems

Self-generated magnetic field in three-dimensional ablative Rayleigh-Taylor instability

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arXiv 2024年

作者： Zhang, Dehua Jiang, Xian Tao, Tao Li, Jun Yan, Rui Sun, De-Jun Zheng, Jian Department of Modern Mechanics University of Science and Technology of China Hefei230026 China Department of Plasma Physics and Fusion Engineering University of Science and Technology of China Anhui Hefei230026 China Institute of Applied Physics and Computational Mathematics Beijing100094 China IFSA Collaborative Innovation Center Shanghai Jiao Tong University Shanghai200240 China

The self-generated magnetic field in three-dimensional (3D) single-mode ablative Rayleigh-Taylor instabilities (ARTI) relevant to the acceleration phase of a direct-drive inertial confinement fusion (ICF) implosion is investigated. It is found that stronger magnetic fields up to a few thousands of T can be generated by 3D ARTI than by its two-dimensional (2D) counterpart. The Nernst effects significantly alter the magnetic fields convection and amplify the magnetic fields. The scaling law for the magnetic flux obtained in the 2D simulations performs reasonably well in the 3D cases. While the magnetic field significantly accelerates the bubble growth in the short-wavelength 2D modes through modifying the heat fluxes, the magnetic field mostly accelerates the spike growth but has little influence on the bubble growth in 3D ARTI. Copyright © 2024, The Authors. All rights reserved.

关键词： Acceleration