The Jeans Instability in Presence of Viscous Effects

TL;DR

This paper investigates how bulk viscosity influences gravitational instability and structure formation, showing that viscosity dampens perturbations and suppresses fragmentation without altering the Jeans mass.

Contribution

It provides a generalized analysis of the Jeans mechanism incorporating viscous effects in an expanding universe within a Newtonian framework.

Findings

Viscous effects damp perturbation growth.

Viscosity suppresses the top-down fragmentation process.

Jeans mass remains unchanged despite viscosity.

Abstract

An analysis of the gravitational instability in presence of dissipative effects is addressed. In particular, the standard Jeans Mechanism and the generalization in treating the Universe expansion are both analyzed when bulk viscosity affects the first-order Newtonian dynamics. As results, the perturbation evolution is founded to be damped by dissipative processes and the top-down mechanism of structure fragmentation is suppressed. In such a scheme, the value of the Jeans Mass remains unchanged also in presence of viscosity.