Bouncing cosmologies in the presence of a Dirac-Born-Infeld field

TL;DR

This paper analyzes how a Dirac-Born-Infeld (DBI) field influences bouncing cosmologies in a closed universe, finding that ultra-relativistic limits and specific potential functions expand initial conditions for bounces.

Contribution

It provides a detailed dynamical system analysis of DBI fields in closed FLRW cosmologies, highlighting conditions that enable bouncing universes and the effects of potential and tension functions.

Findings

Ultra-relativistic DBI fields allow more initial conditions for bounces.

Power-law potentials and tensions increase bounce conditions compared to exponential.

No stable cyclical behavior observed with DBI fields, even with negative cosmological constant.

Abstract

We perform a detailed dynamical system analysis for the behaviour of a Dirac-Born-Infeld (DBI) field in a spatially closed Friedmann-Lema\^itre-Robertson-Walker (FLRW) cosmology. The DBI field is characterised by a potential and brane tension. We study power-law or exponential functions for the potential and tension. We find that in a spatially closed FLRW cosmology, a DBI field in the ultra-relativistic limit allows for a broader range of initial conditions resulting in a bouncing universe than in the non-relativistic limit. We further note that the range of initial conditions allowing for a bounce is larger if we consider power-law functions for the potential and tension, compared to the exponential case. Our dynamical analysis shows that a DBI field does not exhibit stable cyclical behaviour, including the case in which a negative cosmological constant is present.