Cosmological Solution in M-theory on S^1/Z_2

TL;DR

This paper presents the first cosmological solution in Horava-Witten supergravity, showing an expanding universe with boundary-dependent expansion rates, which become isotropic over time due to gravitational effects.

Contribution

It introduces a novel cosmological solution in M-theory on S^1/Z_2 by exchanging time with a transverse coordinate, revealing boundary-dependent expansion dynamics.

Findings

Boundary worlds expand at different rates initially.

Anisotropy diminishes over time due to gravity.

Solution links instanton tunneling to cosmological expansion.

Abstract

We provide the first example of a cosmological solution of the Horava-Witten supergravity. This solution is obtained by exchanging the role of time with the radial coordinate of the transverse space to the five-brane soliton. On the boundary this corresponds to rotating an instanton solution into a tunneling process in a space with Lorentzian signature, leading to an expanding universe. Due to the freedom to choose different non-trivial Yang-Mills backgrounds on the boundaries, the two walls of the universe ( visible and hidden worlds) expand differently. However at late times the anisotropy is washed away by gravitational interactions.