Colliding Branes in Heterotic M-theory

TL;DR

This paper analyzes brane collisions in heterotic M-theory, identifying a unique non-divergent solution with specific local geometry and examining singularities and cosmological implications.

Contribution

It uniquely characterizes the local geometry during brane collision and clarifies the nature of singularities and the relation among various cosmological solutions.

Findings

Identified a unique non-divergent solution near brane collision.

Found that singularities are mild and regularisable.

Unified different cosmological solutions as parts of a single flat solution.

Abstract

We study the collision of two flat, parallel end-of-the-world branes in heterotic M-theory. By insisting that there is no divergence in the Riemann curvature as the collision approaches, we are able to single out a unique solution possessing the local geometry of (2d compactified Milne)/Z_2 x R_3, times a finite-volume Calabi-Yau manifold in the vicinity of the collision. At a finite time before and after the collision, a second type of singularity appears momentarily on the negative-tension brane, representing its bouncing off a zero of the bulk warp factor. We find this singularity to be remarkably mild and easily regularised. The various different cosmological solutions to heterotic M-theory previously found by other authors are shown to merely represent different portions of a unique flat cosmological solution to heterotic M-theory.