D-instantons and Closed String Tachyons in Misner Space

TL;DR

This paper explores how closed string tachyon condensation in Misner space, a model for the big bang, can smooth out singularities, using D-instantons as probes to analyze geometric deformations.

Contribution

It demonstrates the use of D-instantons to study tachyon condensation effects on spacetime geometry in Misner space, revealing a smoothing of singularities.

Findings

Tachyon condensation deforms the Misner space geometry.

D-instantons effectively probe the effects of tachyon condensation.

Singularity becomes milder after tachyon condensation.

Abstract

We investigate closed string tachyon condensation in Misner space, a toy model for big bang universe. In Misner space, we are able to condense tachyonic modes of closed strings in the twisted sectors, which is supposed to remove the big bang singularity. In order to examine this, we utilize D-instanton as a probe. First, we study general properties of D-instanton by constructing boundary state and effective action. Then, resorting to these, we are able to show that tachyon condensation actually deforms the geometry such that the singularity becomes milder.