Brane-world Singularities

TL;DR

This paper explores the nature of singularities in brane-world cosmologies, examining their isotropic or anisotropic characteristics and evaluating the Weyl curvature conjecture within a four-dimensional framework.

Contribution

It provides a detailed analysis of singularity behavior in brane-worlds and discusses the formulation of the Weyl curvature conjecture in a 4D context.

Findings

Singularities can be either isotropic or anisotropic.

The Weyl curvature conjecture is applicable in the brane-world scenario.

Formulation of the conjecture should be in four-dimensional terms.

Abstract

We study the behavior of spatially homogeneous brane-worlds close to the initial singularity in the presence of both local and nonlocal stresses. It is found that the singularity in these brane-worlds can be locally either isotropic or anisotropic. We then investigate the Weyl curvature conjecture, according to which some measure of the Weyl curvature is related to a gravitational entropy. In particular, we study the Weyl curvature conjecture on the brane with respect to the dimensionless ratio of the Weyl invariant and the Ricci square and the measure proposed by Gr{\o}n and Hervik. We also argue that the Weyl curvature conjecture should be formulated on brane (i.e., in the four-dimensional context).