Nonsingular Cosmologies in Presence of String Cloud

TL;DR

This paper explores nonsingular cosmological models in a braneworld scenario with a string cloud in a five-dimensional AdS bulk, analyzing stability and conditions for nonsingular evolution.

Contribution

It introduces a string cloud in the bulk and studies its effects on nonsingular cosmologies and bubble universe stability in braneworld models.

Findings

Nonsingular cosmology can be achieved under specific mass and cosmological parameters.

The bounce in the cosmology occurs inside the Cauchy horizon, indicating instability.

Stable nonsingular bubble universe solutions are possible with certain bulk and bubble parameters.

Abstract

In the braneworld scenario, we introduce a uniformly distributed cloud of infinitely long strings in the five dimensional AdS bulk spacetime. The end points of the strings are attached to the brane and becomes the source of the four dimensional matter on the brane, while the body of the strings hang onto the radial direction of the bulk and act as the gluonic field on the brane. The presence of matter in the brane induces a nonsingular cosmological evolution for the scale factor of the brane world under certain conditions of mass and cosmological parameters. However, the nonsingular nature is unstable since the bounce occurs inside the Cauchy horizon. Further, we consider the shellworld or the dark bubble scenario for the same bulk spacetime. It shows stable nonsingular cosmological nature of the bubble universe under certain conditions on the bulk and bubble parameters.