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Efficient modeling of dispersive materials via time-domain simulations of the Maxwell equations relies on the technique of auxiliary differential equations. In this approach, a material's frequency-dependent permittivity is represented via…

Motivated by previous work on kinetic energy cascades in the ocean and atmosphere, we develop a spatio-temporal spectral transfer tool that can be used to study scales of variability in generalized dynamical systems. In particular, we use…

The study of photoionised gas in planetary nebulae (PNe) has played a major role achieving, over the years, a better understanding of a number of physical processes pertinent to a broader range of fields than just PNe studies, ranging from…

Astrophysics · Physics 2009-11-11 Barbara Ercolano

In this paper we discuss numerical methods and algorithms for the solution of NLTE stellar atmosphere problems involving expanding atmospheres, e.g., found in novae, supernovae and stellar winds. We show how a scheme of nested iterations…

Astrophysics · Physics 2011-06-02 P. H. Hauschildt , E. Baron

We calculate the time dependent electron distribution under the assumption of continuous injection of new relativistic particles, and assuming radiative cooling (by sinchrotron and inverse Compton) and particle escape. Resulting photon…

Astrophysics · Physics 2007-05-23 Marco Chiaberge , Gabriele Ghisellini

Context. The solar irradiance is known to change on time scales of minutes to decades, and it is suspected that its substantial fluctua- tions are partially responsible for climate variations. Aims. We are developing a solar atmosphere code…

Solar and Stellar Astrophysics · Physics 2015-05-18 A. I. Shapiro , W. Schmutz , M. Schoell , M. Haberreiter , E. Rozanov

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 present a specialization of the grid-based implementation of the time-dependent configuration-interaction singles described in the preceding paper (arXiv:2204.09966) to the case of spherical symmetry. We describe the intricate time…

The method of approximate automodel solution for the Green's function of the time-dependent superdiffusive (nonlocal) transport equations (J. Phys. A: Math. Theor. 49 (2016) 255002) is extended to the case of a finite velocity of carriers.…

Statistical Mechanics · Physics 2019-09-04 A. B. Kukushkin , A. A. Kulichenko

Of primary interest in this paper is the numerical approximation of a time dependent fractional, in space, diffusion equation where the domain is assumed to be nonhomogeneous, having different axial diffusion coefficients. This work is…

Numerical Analysis · Mathematics 2026-05-12 T. Catoe , V. J. Ervin

We use multi-frequency radiation hydrodynamics (rad-HD) to simulate radiative acceleration of a spherically symmetric stellar wind. We demonstrate the rad-HD capabilities of Athena++ for a series of test problems with multi-group radiation…

High Energy Astrophysical Phenomena · Physics 2019-11-22 Sergei Dyda , Christopher S. Reynolds , Yan-Fei Jiang

For the time-parallel Parareal method, there exists both numerical and analytical proof that it converges very well for diffusive problems like the heat equation. Many applications, however, do not lead to simple homogeneous diffusive…

Numerical Analysis · Mathematics 2016-03-18 Daniel Ruprecht , Robert Speck , Rolf Krause

A new numerical code, designed for the detailed numerical treatment of nonlinear diffusive shock acceleration, is used for modeling of particle acceleration and radiation in young supernova remnants. The model is based on spherically…

High Energy Astrophysical Phenomena · Physics 2015-05-14 V. N. Zirakashvili , F. A. Aharonian

The remnant of SN 1987A is the best-studied object of its kind. The rich data-set of its thermal and non-thermal emission across the electromagnetic spectrum poses a unique testbed for the elaboration of particle-acceleration theory. We use…

High Energy Astrophysical Phenomena · Physics 2021-09-14 Robert Brose , Jonathan Mackey , Sean Kelly , Nathan Grin , Luca Grassitelli

In order to understand observable signatures from putative cosmic-ray (CR) sources in-source acceleration of particles, their energy and time-dependent transport including interactions in an evolving environment and their escape from source…

High Energy Astrophysical Phenomena · Physics 2023-09-11 A. Reimer , L. Merten , M. Boughelilba , P. Da Vela , S. Vorobiov , J. P. Lundquist

The brightness of the emission from coronal loops in the solar atmosphere is strongly dependent on the temperature and density of the confined plasma. After a release of energy, these loops undergo a heating and upflow phase, followed by a…

Solar and Stellar Astrophysics · Physics 2019-03-20 C. D. Johnston , S. J. Bradshaw

We explore the propagation and transformation of electromagnetic waves through spatially homogeneous yet smoothly time-dependent media within the framework of classical electrodynamics. By modelling the smooth transition, occurring during a…

Three approaches are considered to solve the equation which describes the time-dependent diffusive shock acceleration of test particles at the non-relativistic shocks. At first, the solution of Drury (1983) for the particle distribution…

High Energy Astrophysical Phenomena · Physics 2016-08-31 Oleh Petruk , Bohdan Kopytko

Radiation pressure exerted by solar photon output is salient to the motion of primary neutral hydrogen atoms streaming into the inner heliosphere directly from the Local Interstellar Medium (LISM). The action of a time-dependent radiation…

Solar and Stellar Astrophysics · Physics 2024-04-30 Lucas Dyke , Hans-Reinhard Müller

In this work, we revisit/reinterpret/extend the model-independent analysis method (which we now call spread - luminosity distance fitting, spread-LDF) from our previous work. We apply it to the updated supernova type Ia catalogue, Pantheon+…

General Relativity and Quantum Cosmology · Physics 2025-12-02 A. Kazım Çamlıbel , M. Akif Feyizoğlu , İbrahim Semiz