Cosmic Acceleration Data and Bulk-Brane Energy Exchange

TL;DR

This paper explores a braneworld cosmological model with bulk-brane energy exchange, demonstrating its ability to naturally cross the phantom divide line without phantom energy, supported by analysis of the latest supernova data.

Contribution

It introduces a braneworld model with bulk-brane energy exchange that allows crossing w=-1 without phantom energy, fitting observational data and suggesting a relativistic bulk component.

Findings

Best fit parameters indicate a bulk component behaving like relativistic matter.

Model successfully crosses the phantom divide line w=-1.

Cosmological data favor natural parameter values.

Abstract

We consider a braneworld model with bulk-brane energy exchange. This allows for crossing of the w=-1 phantom divide line without introducing phantom energy with quantum instabilities. We use the latest SnIa data included in the Gold06 dataset to provide an estimate of the preferred parameter values of this braneworld model. We use three fitting approaches which provide best fit parameter values and hint towards a bulk energy component that behaves like relativistic matter which is propagating in the bulk and is moving at a speed v along the fifth dimension, while the bulk-brane energy exchange component corresponds to negative pressure and signifies energy flowing from the bulk into the brane. We find that the best fit effective equation of state parameter $w_{eff}$ marginally crosses the phantom divide line w=-1. Thus, we have demonstrated both the ability of this class of braneworld models to provide crossing of the phantom divide and also that cosmological data hint towards natural values for the model parameters.