Chameleon Effects on Small Scale Structure and the Baryonic Jeans Mass

TL;DR

This paper investigates how chameleon scalar fields influence the baryonic Jeans mass in cosmology, revealing that baryon effects extend to smaller scales than in standard gravity, especially under strong coupling, with observable implications.

Contribution

It introduces the impact of chameleon scalar fields on the baryonic Jeans mass, highlighting differences from general relativity and exploring strong coupling effects.

Findings

Baryon effects persist at smaller scales with chameleon fields.

Strong coupling enhances the influence of scalar fields on structure formation.

Potential observable consequences are identified.

Abstract

In the framework of Newtonian cosmology or general relativity it is simple to derive a mass scale below which collapsed structures are relatively devoid of baryons. We examine how the inclusion of a chameleon scalar field affects this baryonic Jeans mass, bearing in mind both the canonical case of a gravitational-strength coupling between the scalar field and matter, as well as the strong coupling regime wherein the coupling is very large. We find that baryon effects persist down to smaller scales in a chameleon theory than they do in ordinary general relativity, especially in the case of strong coupling. Several potentially observable consequences of this are identified.