New Cosmological Singularities in Braneworld Models

TL;DR

This paper explores unique 'quiescent' cosmological singularities in braneworld models where higher derivatives of the universe's scale factor diverge, despite finite matter density and expansion rate, due to the embedding of the brane in higher dimensions.

Contribution

It introduces and analyzes a new class of singularities in braneworld cosmology characterized by divergence of higher derivatives while matter density remains finite.

Findings

Existence of 'quiescent' singularities in braneworld models.

Singularities can occur during both contraction and expansion phases.

These singularities are due to the brane's embedding in the bulk, even in empty universes.

Abstract

Higher-dimensional braneworld models which contain both bulk and brane curvature terms in the action admit cosmological singularities of rather unusual form and nature. These `quiescent' singularities, which can occur both during the contracting as well as the expanding phase, are characterised by the fact that while the matter density and Hubble parameter remain finite, all higher derivatives of the scale factor ($\stackrel{..}{a}$, $\stackrel{...}{a}$ etc.) diverge as the cosmological singularity is approached. The singularities are the result of the embedding of the (3+1)-dimensional brane in the bulk and can exist even in an empty homogeneous and isotropic (FRW) universe. The possibility that the present universe may expand into a singular state is discussed.