Mirage Cosmology of U(1) Gauge Field on Unstable D3 Brane Universe

TL;DR

This paper explores the cosmological evolution of an unstable D3-brane universe influenced by a tachyon field and U(1) gauge field, revealing how their coupling affects the universe's expansion and density behavior.

Contribution

It introduces a detailed analysis of the coupled tachyon and gauge field dynamics on an unstable D3-brane, highlighting their impact on cosmological evolution and density regulation.

Findings

Minimal coupling reduces divergence of effective brane density.

Tachyon field's regulation effectiveness varies across theory sectors.

Different cosmological models emerge from density dependence on scale factor.

Abstract

An unstable $D3$-brane universe governed by the DBI action of the tachyon field minimally coupled to a U(1) gauge boson is examined. The cosmological evolution of this coupled system, is further analyzed, in terms of the expansion rate of the inflating brane, which is highly affected by the presence of the tachyonic and gauge field charges. We show, that the minimal coupling makes the effective brane density less divergent. However, for some sectors of the theory the tachyon is not able to regulate it in an efficient fashion. Also, a detailed analysis of the dependance of the effective brane density on the scale factor of the universe is performed, which leads to various cosmological models.