Towards a Solution of the Moduli Problems of String Cosmology

TL;DR

This paper addresses key moduli problems in string cosmology by proposing a scenario where all moduli except the dilaton are at enhanced symmetry points, with the dilaton's potential allowing it to reach a stable minimum.

Contribution

It introduces a novel solution where moduli are stabilized at enhanced symmetry points, and the dilaton's potential dynamics prevent cosmological issues.

Findings

Dilaton can find its potential minimum under certain conditions.

Moduli at enhanced symmetry points avoid domination at nucleosynthesis.

Dilaton dynamics do not break supersymmetry.

Abstract

There are at least two serious moduli problems in string cosmology. The first is the possibility that moduli dominate the energy density at the time of nucleosynthesis. The second is that they may not find their minima all together. After reviewing some previously proposed solutions to these problems, we propose another: all of the moduli but the dilaton sit at points of enhanced symmetry. The dilaton has a potential similar to those of racetrack models; it is very massive and its dynamics do not break supersymmetry. The dilaton is able to find the minimum of its potential because the energy is dominated by non-zero momentum modes. This energy need not be thermal. The effective potential for the dilaton is quite different from its flat space form. If certain conditions are satisfied, the dilaton settles into the desired minimum; if not, it is forced to weak coupling.