Stringy Instanton Effects in Models with Rigid Magnetised D-branes

TL;DR

This paper analyzes non-perturbative instanton effects in string theory models with magnetized D-branes, revealing how they generate mass terms and influence gauge symmetry breaking.

Contribution

It provides explicit calculations of instantonic effects in specific orientifold models with magnetized D-branes, including their impact on the low-energy effective action.

Findings

Instantons induce linear terms in charged fields.

Non-perturbative mass terms are generated.

Gauge theories can exhibit conformal symmetry broken by instantons.

Abstract

We compute instantonic effects in globally consistent T^6/Z2xZ2 orientifold models with discrete torsion and magnetised D-branes. We consider fractional branes and instantons wrapping the same rigid cycles. We clarify and analyse in detail the low-energy effective action on D-branes in these models. We provide explicit examples where instantons induce linear terms in the charged fields, or non-perturbative mass terms are generated. We also find examples where the gauge theory on fractional branes has conformal symmetry at one-loop, broken by instantonic mass terms at a hierarchically small energy scale.