Time and space dependent backgrounds from nonsupersymmetric strings

TL;DR

This paper explores nonsupersymmetric string backgrounds with D-branes and O-planes, revealing solutions with controlled string coupling, diverse time and space evolutions, and connections to orbifold geometries.

Contribution

It identifies a class of maximally symmetric nonsupersymmetric string backgrounds with stable string coupling and analyzes their time and space-dependent properties.

Findings

Existence of solutions with perturbative string coupling everywhere

Time evolution solutions exhibiting big-bang singularities

Space-dependent backgrounds with orbifold singularities

Abstract

We investigate maximally symmetric backgrounds in nonsupersymmetric string vacua with D-branes and O-planes localized in the compact space. We find a class of solutions with a perturbative string coupling constant in all regions of spacetime. Depending on the particular model, we find either a time evolution with a big-bang type singularity or a space dependent background with generically orbifold singularities. We show that the result can be interpreted as a supersymmetric bulk with some symmetries broken by the boundaries. We also discuss an interesting connection to Lorentzian and Euclidian orbifolds.