Brane cosmology driven by the rolling tachyon

TL;DR

This paper explores brane cosmology influenced by a rolling tachyon within a Randall-Sundrum framework, showing how low-energy behavior mimics standard cosmology and analyzing the system's qualitative dynamics beyond low energies.

Contribution

It introduces an effective field theory approach to tachyon-driven brane cosmology and examines the system's behavior across different cosmological constant regimes.

Findings

Standard cosmology mimics low-energy tachyon behavior.

For negative effective cosmological constant, the universe ends in a big crunch.

The tachyon does not settle at the potential minimum when _4<0.

Abstract

Brane cosmology driven by the tachyon rolling down to its ground state is investigated. We adopt an effective field theoretical description for the tachyon and Randall-Sundrum type brane world scenario. After formulating basic equations, we show that the standard cosmology with a usual scalar field can mimic the low energy behavior of the system near the tachyon ground state. We also investigate qualitative behavior of the system beyond the low energy regime for positive, negative and vanishing 4-dimensional effective cosmological constant $\Lambda_4=\kappa_5^4V(T_0)^2/12-|\Lambda_5|/2$, where $\kappa_5$ and $\Lambda_5$ are 5-dimensional gravitational coupling constant and (negative) cosmological constant, respectively, and $V(T_0)$ is the (positive) tension of the brane in the tachyon ground state. In particular, for $\Lambda_4<0$ the tachyon never settles down to its potential minimum and the universe eventually hits a big-crunch singularity.