Initial Conditions and the Structure of the Singularity in Pre-Big-Bang Cosmology

TL;DR

This paper explores a pre-big-bang cosmological model where the universe originates from interacting gravitational and dilatonic waves, leading to a singularity with a Kasner-like structure, and discusses conditions for inflation and thermodynamic properties of initial states.

Contribution

It provides an explicit analytic relation between initial wave data and the resulting Kasner exponents, and suggests plane waves as thermodynamically favorable initial conditions.

Findings

Pre-big-bang inflation can occur for a dense set of initial conditions.

Interacting plane waves lead to a Kasner-like singularity.

Plane waves carry zero gravitational entropy, making them suitable initial states.

Abstract

We propose a picture, within the pre-big-bang approach, in which the universe emerges from a bath of plane gravitational and dilatonic waves. The waves interact gravitationally breaking the exact plane symmetry and lead generically to gravitational collapse resulting in a singularity with the Kasner-like structure. The analytic relations between the Kasner exponents and the initial data are explicitly evaluated and it is shown that pre-big-bang inflation may occur within a dense set of initial data. Finally, we argue that plane waves carry zero gravitational entropy and thus are, from a thermodynamical point of view, good candidates for the universe to emerge from.