Moduli (Dilaton, Volume and Shape) Stabilization via Massless F and D String Modes

TL;DR

This paper proposes a string gas cosmology mechanism using massless F- and D-string modes to stabilize the dilaton, volume, and shape moduli of extra dimensions, achieving consistent stabilization without fine tuning.

Contribution

It introduces a novel stabilization method for all key moduli in string theory using massless string modes within a cosmological framework, extending previous models.

Findings

Massless F-string modes stabilize extra dimensions after dilaton stabilization.

Including D-string gases allows simultaneous stabilization of all moduli in bosonic string theory.

The mechanism is robust, phenomenologically consistent, and avoids fine tuning.

Abstract

Finding a consistent way to stabilize the various moduli fields which generically appear in string theory compactifications, is essential if string theory is to make contact with the physics we see around us. We present, in this paper, a mechanism to stabilize the dilaton within a framework that has already proven itself capable of stabilizing the volume and shape moduli of extra dimensions, namely string gas cosmology. Building on previous work, which uncovered the special role played by massless F-string modes in stabilizing extra dimensions once the dilaton has stabilized, we find that the string gas cosmology of such modes also offers a consistent mechanism to stabilize the dilaton itself, given the stabilization of the extra dimensions. We then generalize the model to include D-string gases, and find that in the case of bosonic string theory, it is possible to simultaneously stabilize all the moduli we consider consistent with weak coupling. We find that our stabilization mechanism is robust, phenomenologically consistent and evades certain difficulties which might previously have seemed to generically plague moduli stabilization mechanisms, without the need for any fine tuning.