Applications of String Theory: Non-perturbative Effects in Flux Compactifications and Effective Description of Statistical Systems

TL;DR

This paper explores non-perturbative effects in flux compactifications of string theory and develops effective models for statistical interfaces, combining world-sheet calculations with statistical system analysis.

Contribution

It provides new insights into flux-induced non-perturbative superpotentials in string compactifications and introduces effective string models for statistical interfaces, validated against numerical data.

Findings

Fluxes induce fermionic masses and soft terms in string models.

Fluxes generate new non-perturbative superpotential terms.

Effective string models accurately describe statistical interfaces and match Monte Carlo data.

Abstract

In this paper, which is a revised version of the author's PhD thesis, we analyze two different applications of string theory. In the first part, we focus on four dimensional compactifications of Type II string theories preserving N=1 supersymmetry, in presence of intersecting or magnetized D-branes. We show, through world-sheet methods, how the insertion of closed string background fluxes may modify the effective interactions on Dirichlet and Euclidean branes. In particular, we compute flux-induced fermionic masses. The generality of our results is exploited to determine the soft terms of the action on the instanton moduli space. Finally, we investigate how fluxes create new non-perturbative superpotential terms in presence of gauge and stringy instantons in SQCD-like models. The second part is devoted to the description of statistical systems through effective string models. In particular, we focus our attention on (d-1)-dimensional interfaces, present in particular statistical systems defined on compact d-dimensional spaces. We compute their exact partition function by resorting to standard covariant quantization of the Nambu-Goto theory, and we compare it with Monte Carlo data. Then, we propose an effective model to describe interfaces in 2d space and test it against the dimensional reduction of the Nambu-Goto description of the 2d interface.