Jeans analysis in modified gravity

TL;DR

This paper explores how Modified Gravity (MOG) affects the dynamics and stability of self-gravitating systems, deriving new Jeans criteria and assessing differences from general relativity at various cosmic scales.

Contribution

It derives new Jeans mass and wave-number limits within MOG and compares gravitational instability predictions to general relativity across different astrophysical scales.

Findings

MOG introduces modified Jeans mass and wave-number limits.

No significant difference between MOG and GR in star-forming regions.

Potential differences between MOG and GR at intergalactic scales.

Abstract

MOdified Gravity (MOG) is a covariant modification of Einstein's general relativity. This theory is one of the current alternatives to dark matter models. We describe dynamics of collisionless self-gravitating systems in the context of MOG. By studying the weak field approximation of this theory, we derive the equations governing the dynamics of the self-gravitating systems. More specifically, we consider the Jeans instability for self-gravitating fluid and stellar systems, and derive new Jeans mass limit $\tilde{M}_J$ and wave-number $\tilde{k}_J$. Furthermore, considering the gravitational instability in star forming regions, we show that MOG has not a significant difference with general relativity on this astrophysical scale. However, at larger scales such as intergalactic space MOG may lead to different galaxy and structure formation processes.