The Relic Problem of String Gas Cosmology

TL;DR

This paper examines the relic problem in string gas cosmology, highlighting issues with relics like gravitinos and monopoles, and discusses potential solutions including reheating and inflation, with implications for the theory's success.

Contribution

It identifies the relic overproduction problem in SGC and proposes inflation as a solution to the monopole issue, analyzing the impact on SGC's explanatory power.

Findings

Relics are produced copiously near the Hagedorn temperature.

Reheating can solve the gravitino problem but not monopoles.

Inflation can dilute monopoles but diminishes SGC's other achievements.

Abstract

We discuss the relic problem of string gas cosmology (SGC) using gravitinos and magnetic monopoles as examples. Since SGC operates near or at the Hagedorn temperature, relics are produced copiously; in the absence of dilution, their abundances are too large. A subsequent phase of reheating can solve the gravitino problem, but fails to dilute monopoles sufficiently. We propose a subsequent phase of inflation as the most natural solution to the monopole problem; unfortunately, inflation marginalizes almost all potential achievements of SGC, with the exception of a possible explanation of the dichotomy of space (why did only three dimensions inflate?).