Bare and effective fluid description in brane world cosmology

TL;DR

This paper explores an effective fluid approach in five-dimensional brane world cosmology, revealing diverse scenarios where the effective equation of state significantly differs from the bare one, including crossing the phantom divide.

Contribution

It introduces a novel effective fluid framework for brane cosmology that accounts for both positive and negative brane tensions, highlighting new cosmological behaviors.

Findings

Effective fluid can cross the  barrier for negative brane tension.

Effective equations differ significantly from bare equations in various scenarios.

Multiple cosmological models with distinct behaviors are identified.

Abstract

An effective fluid description, for a brane world model in five dimensions, is discussed for both signs of the brane tension. We found several cosmological scenarios where the effective equation differs widely from the bare equation of state. For universes with negative brane tension, with a bare fluid satisfying the strong energy condition, the effective fluid can cross the barrier $\omega _{eff} =-1$.