Non-Newtonian corrections to radiative viscosity: Israel-Stewart theory as a viscosity limiter

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1. Verfasser: Gavassino, Lorenzo
Format: Preprint
Veröffentlicht: 2024
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author Gavassino, Lorenzo
author_facet Gavassino, Lorenzo
contents Radiation is a universal friction-increasing agent. When two fluid layers are in relative motion, the inevitable exchange of radiation between such layers gives rise to an effective force, which tries to prevent the layers from sliding. This friction is often modeled as a Navier-Stokes shear viscosity. However, non-Newtonian corrections are expected to appear at distances of about one optical depth from the layers' interface. Such corrections prevent the viscous stress from becoming too large. Here, we set the foundations of a rigorous theory for these corrections, valid along incompressible flows. We show that, in the linear regime, the infinite Chapman-Enskog series can be computed analytically, leading to universal formulas for all transport coefficients, which apply to any fluid, with any composition, with radiation of any type (also neutrinos), and with nearly any type of radiative process. We then show that, with an appropriate shear-heat coupling coefficient, Israel-Stewart theory can correctly describe most non-Newtonian features of radiative shear stresses.
format Preprint
id arxiv_https___arxiv_org_abs_2411_12929
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Non-Newtonian corrections to radiative viscosity: Israel-Stewart theory as a viscosity limiter
Gavassino, Lorenzo
High Energy Astrophysical Phenomena
General Relativity and Quantum Cosmology
Nuclear Theory
Radiation is a universal friction-increasing agent. When two fluid layers are in relative motion, the inevitable exchange of radiation between such layers gives rise to an effective force, which tries to prevent the layers from sliding. This friction is often modeled as a Navier-Stokes shear viscosity. However, non-Newtonian corrections are expected to appear at distances of about one optical depth from the layers' interface. Such corrections prevent the viscous stress from becoming too large. Here, we set the foundations of a rigorous theory for these corrections, valid along incompressible flows. We show that, in the linear regime, the infinite Chapman-Enskog series can be computed analytically, leading to universal formulas for all transport coefficients, which apply to any fluid, with any composition, with radiation of any type (also neutrinos), and with nearly any type of radiative process. We then show that, with an appropriate shear-heat coupling coefficient, Israel-Stewart theory can correctly describe most non-Newtonian features of radiative shear stresses.
title Non-Newtonian corrections to radiative viscosity: Israel-Stewart theory as a viscosity limiter
topic High Energy Astrophysical Phenomena
General Relativity and Quantum Cosmology
Nuclear Theory
url https://arxiv.org/abs/2411.12929