Non-Abelian brane cosmology

TL;DR

This paper explores how non-Abelian Born-Infeld matter influences isotropic, homogeneous D-brane cosmology, revealing unique expansion behaviors and presenting a cosmological sphaleron solution within the brane-world framework.

Contribution

It introduces the effects of non-Abelian Born-Infeld matter on brane cosmology, including the equation of state and evolution laws, and presents a new cosmological sphaleron solution.

Findings

NBI matter leads to a string gas-like equation of state with zero acceleration.

The brane-world evolution mimics conformal symmetry restoration.

A new cosmological sphaleron solution on the D-brane is provided.

Abstract

We discuss isotropic and homogeneous D-brane-world cosmology with non-Abelian Born-Infeld (NBI) matter on the brane. In the usual Friedmann-Robertson-Walker (FRW) model the scale non-invariant NBI matter gives rise to an equation of state which asymptotes to the string gas equation $p=-\epsilon/3$ and ensures a start-up of the cosmological expansion with zero acceleration. We show that the same state equation in the brane-world setup leads to the Tolman type evolution as if the conformal symmetry was effectively restored. This is not precisely so in the NBI model with symmetrized trace, but the leading term in the expansion law is still the same. A cosmological sphaleron solution on the D-brane is presented.