Dynamical Cobordism and the Beginning of Time: Supercritical Strings and Tachyon Condensation

TL;DR

This paper explores the concept of the beginning of time in supercritical string theories by modeling timelike dilaton backgrounds as Dynamical Cobordisms, linking singularities to tachyon condensation and bubbles of nothing.

Contribution

It introduces a novel interpretation of the universe's beginning as a Dynamical Cobordism related to tachyon condensation in supercritical strings.

Findings

Timelike linear dilaton backgrounds are described as Dynamical Cobordisms.

The beginning of time is linked to strong coupling tachyon condensation.

Bubbles of nothing are characterized as lightlike Dynamical Cobordisms.

Abstract

We describe timelike linear dilaton backgrounds of supercritical string theories as time-dependent Dynamical Cobordisms in string theory, with their spacelike singularity as a boundary defining the beginning of time. We propose and provide compelling evidence that its microscopic interpretation corresponds to a region of (a strong coupling version of) closed tachyon condensation. We argue that this beginning of time is closely related to (and shares the same scaling behaviour as) the bubbles of nothing obtained in a weakly coupled background with lightlike tachyon condensation. As an intermediate result, we also provide the description of the latter as lightlike Dynamical Cobordism.