The Jeans Mechanism and Bulk-Viscosity Effects

TL;DR

This paper investigates how bulk viscosity influences gravitational instability and fragmentation in Newtonian dynamics, showing damping effects on perturbations but unchanged Jeans mass.

Contribution

It introduces the analysis of bulk-viscosity effects into the classical Jeans mechanism within Newtonian gravity, highlighting damping effects and the preservation of the Jeans mass.

Findings

Viscous effects damp perturbation growth.

Strong viscosity suppresses top-down fragmentation.

Jeans mass remains unchanged with viscosity.

Abstract

In this paper we study the gravitational instability in presence of viscosity. In particular, the standard Jeans Mechanism is analyzed taking into account bulk-viscosity effects in the first-order Newtonian dynamics. We show how the perturbation evolution is damped by dissipative processes and the top-down fragmentation mechanism is suppressed for strong viscous effects. The critical value of the Jeans Mass remains unchanged also in presence of bulk viscosity.