Null cosmological singularities and free strings

TL;DR

This paper investigates free string behavior near null Kasner-like cosmological singularities, finding conditions under which the wavefunctional remains nonsingular and analyzing string excitation in regulated nonsingular regions.

Contribution

It extends previous work by analyzing the string wavefunctional near singularities and exploring string spectra in regulated nonsingular backgrounds.

Findings

Wavefunctional is nonsingular for certain Kasner exponents.

String modes can be solved exactly near singularities.

String excitations increase in regulated nonsingular regions.

Abstract

We continue exploring free strings in the background of null Kasner-like cosmological singularities, following arXiv:0904.4532 [hep-th]. We study the free string Schrodinger wavefunctional along the lines of arXiv:0807.1517 [hep-th]. We find the wavefunctional to be nonsingular in the vicinity of singularities whose Kasner exponents satisfy certain relations. We compare this with the description in other variables. We then study certain regulated versions of these singularities where the singular region is replaced by a substringy but nonsingular region and study the string spectra in these backgrounds. The string modes can again be solved for exactly, giving some insight into how string oscillator states get excited near the singularity.