Topology and Signature Changes in Braneworlds

TL;DR

This paper demonstrates that in braneworld models, topology and signature changes of the universe can occur smoothly without singularities, contrasting with traditional views that such changes require singular events.

Contribution

It introduces explicit examples showing topology and signature changes as smooth classical events within the braneworld framework, using the Dirac-Born-Infeld action.

Findings

Topology change achieved via self-intersecting branes

Signature change occurs in a Lorentzian bulk without singularities

Boundary of signature change appears as a curvature singularity from the brane perspective

Abstract

It has been believed that topology and signature change of the universe can only happen accompanied by singularities, in classical, or instantons, in quantum, gravity. In this note, we point out however that in the braneworld context, such an event can be understood as a classical, smooth event. We supply some explicit examples of such cases, starting from the Dirac-Born-Infeld action. Topology change of the brane universe can be realised by allowing self-intersecting branes. Signature change in a braneworld is made possible in an everywhere Lorentzian bulk spacetime. In our examples, the boundary of the signature change is a curvature singularity from the brane point of view, but nevertheless that event can be described in a completely smooth manner from the bulk point of view.