Cosmic Super-Strings and Kaluza-Klein Modes

TL;DR

This paper investigates how cosmic super-strings emit Kaluza-Klein modes, constraining their properties through astrophysical observations and highlighting their role in cosmic evolution.

Contribution

It provides a detailed analysis of KK mode production by cosmic super-strings and derives observational constraints on their parameters.

Findings

KK emission energy is comparable in different internal space geometries

Astrophysical constraints exclude certain super-string parameter regions

KK modes influence the early evolution of cosmic super-strings

Abstract

Cosmic super-strings interact generically with a tower of relatively light and/or strongly coupled Kaluza-Klein (KK) modes associated with the geometry of the internal space. In this paper, we study the production of spin-2 KK particles by cusps on loops of cosmic F- and D-strings. We consider cosmic super-strings localized either at the bottom of a warped throat or in a flat internal space with large volume. The total energy emitted by cusps in KK modes is comparable in both cases, although the number of produced KK modes may differ significantly. We then show that KK emission is constrained by the photo-dissociation of light elements and by observations of the diffuse gamma ray background. We show that this rules out regions of the parameter space of cosmic super-strings that are complementary to the regions that can be probed by current and upcoming gravitational wave experiments. KK modes are also expected to play an important role in the friction-dominated epoch of cosmic super-string evolution.