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Photodissociation regions (PDRs) define the transition zone between an ionized and a dark molecular region. They consist of neutral gas which interacts with far-ultraviolet radiation and are characterized by strong infrared line emission.…

Solar and Stellar Astrophysics · Physics 2015-06-11 T. G. Bisbas , T. A. Bell , S. Viti , J. Yates , M. J. Barlow

We report homogeneous spectroscopic determinations of the effective temperature, metallicity, and projected rotational velocity for the host stars of 56 transiting planets. Our analysis is based primarily on the Stellar Parameter…

This work describes a new 1D hybrid approach for modeling atmospheric pressure discharges featuring complex chemistry. In this approach electrons are described fully kinetically using Particle-In-Cell/Monte-Carlo (PIC/MCC) scheme, whereas…

Plasma Physics · Physics 2016-01-20 Denis Eremin , Torben Hemke , Thomas Mussenbrock

We present new methods for radiative transfer on hierarchial grids. We develop a new method for calculating the scattered flux that employs the grid structure to speed up the computation. We describe a novel subiteration algorithm that can…

Instrumentation and Methods for Astrophysics · Physics 2015-06-05 T. Lunttila , M. Juvela

Radiative shocks are shocks in a gas where the radiative energy and flux coming from the very hot post-shock material are non-negligible in the shock's total energy budget, and are often large enough to heat the material ahead of the shock.…

High Energy Astrophysical Phenomena · Physics 2015-06-15 N. Vaytet , M. Gonzalez , E. Audit , G. Chabrier

Context: Rotational CO transitions, while acting as a foreground for [C II] line-intensity mapping (LIM) experiments, trace the physical conditions of cold gas in galaxies at lower redshifts. Studying these transitions is also crucial for…

Cosmology and Nongalactic Astrophysics · Physics 2026-03-04 Mathilde Van Cuyck , Matthieu Bethermin , Guilaine Lagache , Alexandre Beelen

We describe the Stagger Code for simulations of magneto-hydrodynamic (MHD) systems. This is a modular code with a variety of physics modules that will let the user run simulations of deep stellar atmospheres, sunspot formation, stellar…

Instrumentation and Methods for Astrophysics · Physics 2024-05-07 Robert F. Stein , Åke Nordlund , Remo Collet , Regner Trampedach

In this article we propose a numerical algorithm to compute the intensity and polarization of a polychromatic electromagnetic radiation crossing a medium with graded refractive index and modeled by the Vector Radiative Refractive Transfer…

Analysis of PDEs · Mathematics 2024-08-06 Olivier Pironneau

Understanding the mechanisms and spatial correlations of crystallographic symmetry breaking in ferroelectric materials is essential to tuning their functional properties. While optical second harmonic generation (SHG) has long been utilized…

Materials Science · Physics 2022-08-10 Wei Li , Yunpeng Ma , Tianyi Feng , Sergei V. Kalinin , Jing-Feng Li , Qian Li

Atomic line opacities play a crucial role in stellar astrophysics. They strongly modify the radiative transfer in stars, therefore impacting their physical structure. Ultimately, most of our knowledge of stellar population systems (stars,…

Solar and Stellar Astrophysics · Physics 2015-06-19 Lucimara Martins , Paula Coelho , Anderson Caproni , Roberto Vitoriano

Starting from the radiative transfer equation and its usual boundary conditions, the objective of this work is to design Monte Carlo algorithms estimating the specific intensity spatial and angular derivatives as well as its geometric…

As an alternative approach for predicting complex dynamical systems where physics-based models are no longer reliable, reservoir computing (RC) has gained popularity. The hybrid approach is considered an interesting option for improving the…

Machine Learning · Computer Science 2025-01-21 Tamon Nakano , Sebastian Baur , Christoph Räth

We develop a new relativistic radiation hydrodynamics code based on the Monte-Carlo algorithm. In this code, we implement a new scheme to achieve the second-order accuracy in time in the limit of a large packet number for solving the…

High Energy Astrophysical Phenomena · Physics 2023-02-15 Kyohei Kawaguchi , Sho Fujibayashi , Masaru Shibata

We evaluate an efficient overset grid method for two-dimensional and three-dimensional particulate flows for small numbers of particles at finite Reynolds number. The rigid particles are discretised using moving overset grids overlaid on a…

Computational Physics · Physics 2017-05-24 A. R. Koblitz , S. Lovett , N. Nikiforakis , W. D. Henshaw

Sparse coding (SC) is attracting more and more attention due to its comprehensive theoretical studies and its excellent performance in many signal processing applications. However, most existing sparse coding algorithms are nonconvex and…

Machine Learning · Computer Science 2017-09-12 Xiaodong Feng , Zhiwei Tang , Sen Wu

To make relevant predictions about observable emission, hydrodynamical simulation codes must employ schemes that account for radiative losses, but the large dimensionality of accurate radiative transfer schemes is often prohibitive.…

Instrumentation and Methods for Astrophysics · Physics 2015-06-23 James C. Lombardi , William G. McInally , Joshua A. Faber

Row-merged polar codes are a family of pre-transformed polar codes (PTPCs) with little precoding overhead. Providing an improved distance spectrum over plain polar codes, they are capable to perform close to the finite-length capacity…

Information Theory · Computer Science 2023-12-25 Andreas Zunker , Marvin Geiselhart , Lucas Johannsen , Claus Kestel , Stephan ten Brink , Timo Vogt , Norbert Wehn

Large scale calculations for the energy levels, transition rates, oscillator strengths, hyperfine interaction constants, Land\'e g$_J$ factors and isotope shifts have been performed for $1s^2$ and $1snl \: (n=2-8 $ and $l \leq (n-1) )$…

Atomic Physics · Physics 2024-01-15 Shikha Rathi , Lalita Sharma

We analyze a class of high performance, low decoding-data-flow error-correcting codes suitable for high bit-rate optical-fiber communication systems. A spatially-coupled split-component ensemble is defined, generalizing from the most…

Information Theory · Computer Science 2015-12-04 Lei M. Zhang , Dmitri Truhachev , Frank Kschischang

Fine-structure transitions can be involved in various processes including photon absorption, charge transfer and inelastic collision between ions, electrons and neutral atoms. We present fine-structure excitation and relaxation cross…

Atomic Physics · Physics 2024-12-10 Pei-Gen Yan , James F. Babb
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