Cosmological String Gas on Orbifolds

TL;DR

This paper investigates how pseudo-wound strings behave on orbifolds, using numerical simulations to understand their persistence and potential impact on cosmological dynamics beyond simple toroidal models.

Contribution

It extends cosmological string studies from toroidal to orbifold compactifications and analyzes the unwinding timescales of pseudo-wound strings through simulations.

Findings

Pseudo-wound strings can last for many Hubble times on orbifolds.

Pseudo-wound strings may influence cosmological evolution similarly to genuine wound strings.

Orbifolds with trivial fundamental group can support long-lived pseudo-wound strings.

Abstract

It has long been known that strings wound around incontractible cycles can play a vital role in cosmology. In particular, in a spacetime with toroidal spatial hypersurfaces, the dynamics of the winding modes may help yield three large spatial dimensions. However, toroidal compactifications are phenomenologically unrealistic. In this paper we therefore take a first step toward extending these cosmological considerations to $D$-dimensional toroidal orbifolds. We use numerical simulation to study the timescales over which "pseudo-wound" strings unwind on these orbifolds with trivial fundamental group. We show that pseudo-wound strings can persist for many ``Hubble times'' in some of these spaces, suggesting that they may affect the dynamics in the same way as genuinely wound strings. We also outline some possible extensions that include higher-dimensional wrapped branes.