A Dynamical Mechanism for Large Volumes with Consistent Couplings

TL;DR

This paper proposes a mechanism to stabilize large extra dimensions in string theory by balancing vacuum energy with non-perturbative effects, ensuring consistent gauge couplings and simplifying stabilization analysis.

Contribution

It introduces a novel dynamical mechanism for large volume stabilization in heterotic string models using non-perturbative physics and modular symmetries.

Findings

Stable minima with consistent gauge couplings are achievable.

Modular symmetries provide consistency checks and aid in tracking soft-terms.

Large UV-IR separation simplifies the stabilization process.

Abstract

A mechanism for addressing the 'decompactification problem' is proposed, which consists of balancing the vacuum energy in Scherk-Schwarzed theories against contributions coming from non- perturbative physics. Universality of threshold corrections ensures that, in such situations, the stable minimum will have consistent gauge couplings for any gauge group that shares the same N = 2 beta function for the bulk excitations as the gauge group that takes part in the minimisation. Scherk- Schwarz compactification from 6D to 4D in heterotic strings is discussed explicitly, together with two alternative possibilities for the non-perturbative physics, namely metastable SQCD vacua and a single gaugino condensate. In the former case, it is shown that modular symmetries gives various consistency checks, and allow one to follow soft-terms, playing a similar role to R-symmetry in global SQCD. The latter case is particularly attractive when there is nett Bose-Fermi degeneracy in the massless sector. In such cases, because the original Casimir energy is generated entirely by excited and/or non-physical string modes, it is completely immune to the non-perturbative IR physics. The large separation between UV and IR contributions to the potential greatly simplifies the analysis of stabilisation, and is a general possibility that has not been considered before.