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We present a novel generalization of the two-stream method of radiative transfer, which allows for the accurate treatment of radiative transfer in the presence of strong infrared scattering by aerosols. We prove that this generalization…

Earth and Planetary Astrophysics · Physics 2017-10-04 Kevin Heng , Daniel Kitzmann

The current paper is concerned with positive stationary solutions and spatial spreading speeds of KPP type evolution equations with random or nonlocal or discrete dispersal in locally spatially inhomogeneous media. It is shown that such an…

Dynamical Systems · Mathematics 2014-11-07 Liang Kong , Wenxian Shen

Exact analytic solutions are derived for radiation in time-dependent relativistic flows. The flows are spherically-symmetric homologous explosions or implosions of matter with a grey extinction coefficient. The solutions are suitable for…

Astrophysics · Physics 2009-11-10 L. B. Lucy

We interpret the Lorentz force equation as a geodesic equation associated with a non-linear connection. Using a geometric averaging procedure, we prove that for narrow and smooth one-particle distribution functions whose supports are…

Mathematical Physics · Physics 2024-11-07 Ricardo Gallego Torrome

A rapid predictive tool based on the linearised Reynolds-averaged Navier-Stokes equations is proposed in this work to investigate secondary currents generated by streamwise-independent surface topography modulations in turbulent channel…

Fluid Dynamics · Physics 2022-07-13 Gerardo Zampino , Davide Lasagna , Bharathram Ganapathisubramani

Several uniqueness results for non-compact complete stationary spacelike surfaces in an $n(\geq 3)$-dimensional Generalized Robertson Walker spacetime are obtained. In order to do that, we assume a natural inequality involving the Gauss…

Differential Geometry · Mathematics 2021-09-08 Danilo Ferreira , Eraldo A. Lima , Alfonso Romero

This paper is devoted to the investigation of spatial spreading speeds and traveling wave solutions of monostable evolution equations with nonlocal dispersal in time and space periodic habitats. It has been shown in an earlier work by the…

Dynamical Systems · Mathematics 2014-12-09 Nar Rawal , Wenxian Shen , Aijun Zhang

Accurate radiative transfer coefficients (emissivities, absorptivities, and rotativities) are needed for modeling radiation from relativistically hot, magnetized plasmas such as those found in Event Horizon Telescope sources. Here we…

High Energy Astrophysical Phenomena · Physics 2021-11-03 Andrew Marszewski , Ben S. Prather , Abhishek V. Joshi , Alex Pandya , Charles F. Gammie

We develop new variational principles to study stability and equilibrium of axisymmetric flows. We show that there is an infinite number of steady state solutions. We show that these steady states maximize a (non-universal) $H$-function. We…

Fluid Dynamics · Physics 2016-08-16 Nicolas Leprovost , Bérengère Dubrulle , Pierre-Henri Chavanis

Stability of the traveling wave solution to a general class of one-dimensional nonlocal evolution equations is studied in $L^2$-spaces, thereby providing an alternative approach to the usual spectral analysis with respect to the supremum…

Probability · Mathematics 2020-01-16 Eva Lang , Wilhelm Stannat

Using theoretical and numerical arguments we discuss some of the commonly accepted approximations for the radiative transfer equations in climatology.

Analysis of PDEs · Mathematics 2021-11-30 Claude Bardos , Francois Golse , Olivier Pironneau

We compute the exact solutions of the radiative transfer equation in two dimensions for isotropic scattering. The intensity and the radiance are given in the space-time domain for isotropic and unidirectional sources. These analytical…

Statistical Mechanics · Physics 2017-03-17 Vincent Rossetto

We consider the two-dimensional Euler equation with periodic boundary conditions. We construct time quasi-periodic solutions of this equation made of localized travelling profiles with compact support propagating over a stationary state…

Analysis of PDEs · Mathematics 2012-03-19 Nicolas Crouseilles , Erwan Faou

We investigate fluid transport in random velocity fields with unsteady drift. First, we propose to quantify fluid transport between flow regimes of different characteristic motion, by escape probability and mean residence time. We then…

chao-dyn · Physics 2007-05-23 Jinqiao Duan , James Brannan , Vincent Ervin

In this paper Einstein's field equations, for static spherically symmetric perfect fluid models with a linear barotropic equation of state, are recast into a 3-dimensional regular system of ordinary differential equations on a compact state…

General Relativity and Quantum Cosmology · Physics 2009-10-31 U. S. Nilsson , C. Uggla

This article presents a set of spectro-goniometric measurements of different water ice samples and the comparison with an approximated radiative transfer model. The experiments were done using the spectro-radiogoniometer described in…

Nonlinear diffusion equations of spectral transfer are systematically derived for anisotropic magnetohydrodynamics in the regime of wave turbulence. The background of the analysis is the asymptotic Alfv\'en wave turbulence equations from…

Solar and Stellar Astrophysics · Physics 2015-05-19 Sebastien Galtier , Eric Buchlin

Using spatial domain techniques developed by the authors and Myunghyun Oh in the context of parabolic conservation laws, we establish under a natural set of spectral stability conditions nonlinear asymptotic stability with decay at Gaussian…

Analysis of PDEs · Mathematics 2015-05-18 Mathew Johnson , Kevin Zumbrun

The study of passive scalar transport in a turbulent velocity field leads naturally to the notion of generalized flows which are families of probability distributions on the space of solutions to the associated ODEs, which no longer satisfy…

Chaotic Dynamics · Physics 2009-10-31 Weinan E , Eric Vanden Eijnden

Solving the null geodesic equations for a ray of light is a difficult task even considering a stationary spacetime. The problem becomes even more difficult if the electromagnetic signal propagates through a flowing optical medium. Indeed,…

General Relativity and Quantum Cosmology · Physics 2024-03-25 Adrien Bourgoin , Pierre Teyssandier , Paolo Tortora , Marco Zannoni