Reflection symmetry breaking scenarios with minimal gauge form coupling in brane world cosmology

TL;DR

This paper explores how breaking reflection symmetry in brane world cosmology affects the geometry and dynamics, showing that certain classical theorems still hold with added parameters for gauge coupling and asymmetry.

Contribution

It extends brane world models by analyzing the effects of reflection symmetry breaking with minimal gauge coupling, generalizing the Friedmann equation and discussing phenomenological implications.

Findings

Generalized Birkhoff theorem remains valid with gauge coupling.

Modified Friedmann equation includes new parameters for gauge strength and asymmetry.

Phenomenological constraints on model parameters are derived.

Abstract

This article synthesises and extends recent work on the cosmological consequences of dropping the usual Z_2 reflection symmetry postulate in brane world scenarios. It is observed that for a cosmological model of homogeneous isotropic type, the relevant generalised Birkhoff theorem establishing staticity of the external vacuum in the maximally symmetric ``bulk'' outside a freely moving world brane will remain valid for the case of motion that is forced by minimal (generalised Wess Zumino type) coupling to an external antisymmetric gauge field provided its kinetic action contribution has the usual homogeneous quadratic form. This means that the geometry on each side of the brane worldsheet will still be of the generalised Schwarzschild anti de Sitter type. The usual first integrated Friedmann equation for the Hubble expansion rate can thereby be straightforwardly generalised by inclusion of new terms involving 2 extra parameters respectively measuring the strength of the gauge coupling and the degree of deviation from reflection symmetry. Some conceivable phenomenological implications are briefly outlined, and corresponding limitations are derived for possible values of relevant parameters.