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A new group of reduced-order models (ROMs) for nonlinear thermal radiative transfer (TRT) problems is presented. They are formulated by means of the nonlinear projective approach and data compression techniques. The nonlinear projection is…

Numerical Analysis · Mathematics 2024-03-12 Joseph M. Coale , Dmitriy Y. Anistratov

We construct a relativistic resistive magneto-hydrodynamic (RRMHD) numerical simulation code for high-energy heavy-ion collisions. We split the system of differential equations into two parts, a non-stiff and a stiff part. For the non-stiff…

Nuclear Theory · Physics 2023-04-05 Kouki Nakamura , Takahiro Miyoshi , Chiho Nonaka , Hiroyuki R. Takahashi

We present a new multi-dimensional radiation-hydrodynamics code for massive stellar core-collapse in full general relativity (GR). Employing an M1 analytical closure scheme, we solve spectral neutrino transport of the radiation energy and…

High Energy Astrophysical Phenomena · Physics 2016-03-09 Takami Kuroda , Tomoya Takiwaki , Kei Kotake

We present a newly developed cosmological hydrodynamics code based on weighted essentially non-oscillatory (WENO) schemes for hyperbolic conservation laws. WENO is a higher order accurate finite difference scheme designed for problems with…

Astrophysics · Physics 2009-11-10 Long-Long Feng , Chi-Wang Shu , Meng-Ping Zhang

We have developed a new computer code, RAM, to solve the conservative equations of special relativistic hydrodynamics (SRHD) using adaptive mesh refinement (AMR) on parallel computers. We have implemented a characteristic-wise, finite…

Astrophysics · Physics 2009-11-11 Weiqun Zhang , Andrew I. MacFadyen

We present a relativistic quantum simulation framework for modeling hydrogen sulfide (H2S) decomposition relevant to hydrogen energy applications. The approach integrates Dirac-Coulomb relativistic quantum chemistry with the variational…

Quantum Physics · Physics 2025-04-16 Chi-Chuan Hwang , Cheng-Fang Su , Jung-Fan Yang

We introduce the radiative transfer postprocessing code Subsweep. The code is based on the method of transport sweeps, in which the exact solution to the scattering-less radiative transfer equation is computed in a single pass through the…

Instrumentation and Methods for Astrophysics · Physics 2024-12-03 Toni Peter , Joseph S. W. Lewis , Ralf S. Klessen , Simon C. O. Glover , Guido Kanschat

We present the open-source radiative transfer code named HELIOS, which is constructed for studying exoplanetary atmospheres. In its initial version, the model atmospheres of HELIOS are one-dimensional and plane-parallel, and the equation of…

We present numerical computations and analysis of atomic to molecular (HI-to-H$_2$) transitions in cool ($\sim$100 K) low-metallicity dust-free (primordial) gas, in which molecule formation occurs via cosmic-ray driven negative ion…

Astrophysics of Galaxies · Physics 2021-10-27 Amiel Sternberg , Alon Gurman , Shmuel Bialy

We introduce an exactly solvable statistical-mechanical model of the hydration of non-polar compounds, based on grouping water molecules in clusters where hydrogen bonds and isotropic interactions occur; interactions between clusters are…

Statistical Mechanics · Physics 2009-11-07 Pierpaolo Bruscolini , Lapo Casetti

Large-scale cosmological simulations of galaxy formation currently do not resolve the densities at which molecular hydrogen forms, implying that the atomic-to-molecular transition must be modeled either on the fly or in postprocessing. We…

A generalization of implicit conservative numerics to multiple dimensions requires advanced concepts of tensor analysis and differential geometry and hence a more thorough dedication to mathematical fundamentals than maybe expected at first…

Instrumentation and Methods for Astrophysics · Physics 2012-10-19 Harald Höller

Attosecond chemistry involves developing strategies to manipulate electronic coherent waves in molecules, which can influence the outcome of photoinduced reactions. While recent progress in this field calls for investigations of…

Chemical Physics · Physics 2026-04-22 Evan Munaro-Langloÿs , Franck Lépine , Victor Despré

We have constructed three-dimensional models for the equilibrium abundance of molecular hydrogen within diffuse interstellar clouds of arbitrary geometry that are illuminated by ultraviolet radiation. The position-dependent photo-…

Astrophysics · Physics 2009-10-30 Marco Spaans , David A. Neufeld

We have developed a modular semi-numerical code that computes the time and spatially dependent ionization of neutral hydrogen (HI), neutral (HeI) and singly ionized helium (HeII) in the intergalactic medium (IGM). The model accounts for…

Cosmology and Nongalactic Astrophysics · Physics 2018-05-02 Anne Hutter

We propose a novel mathematical method to construct an exact polytropic sphere in self-gravitating hydrostatic equilibrium, improving the non-linear Poisson equation. The central boundary condition for the present equation requires a ratio…

Astrophysics · Physics 2009-11-07 Mitsuru Honda , Yasuko. S. Honda

A finite-dimensional chemistry model with two two-level artificial atoms on quantum dots positioned in optical cavities, called the association-dissociation model of neutral hydrogen molecule, is described. The initial circumstances that…

Quantum Physics · Physics 2024-06-08 Hui-hui Miao , Ozhigov Yuri Igorevich

Energy-changing electron-hydrogen atom collisions are crucial to regulating the energy balance in astrophysical and laboratory plasmas and relevant to the formation of stellar atmospheres, recombination in H-II clouds, primordial…

Instrumentation and Methods for Astrophysics · Physics 2015-06-17 Daniel Vrinceanu , Roberto Onofrio , Hossein R. Sadeghpour

In this series of papers we study the structure of the atomic to molecular transition in the giant atomic-molecular complexes that are the repositories of most molecular gas in galaxies, with the ultimate goal of attaining a better…

Astrophysics · Physics 2009-11-13 Mark R. Krumholz , Christopher F. McKee , Jason Tumlinson

We present first results of the evolution of cold cosmic gas obtained through a set of state-of-the-art numerical simulations (ColdSIM). We model time-dependent atomic and molecular non-equilibrium chemistry coupled to HI and H$_2$…

Astrophysics of Galaxies · Physics 2022-02-09 U. Maio