Nonlinear N=2 Supersymmetry, Effective Actions and Moduli Stabilization

TL;DR

This paper uses nonlinear supersymmetry to derive the effective D-brane action in type I string theory, revealing how different contributions to the scalar potential lead to various classes of vacua with stabilized moduli.

Contribution

It provides a comprehensive form of the effective D-brane action incorporating nonlinear supersymmetry and explores the resulting vacuum structures and moduli stabilization mechanisms.

Findings

Identifies three classes of vacua: supersymmetric, anti-de Sitter, and non-supersymmetric with positive energy.

Shows how FI terms and scalar VEVs influence vacuum stability and supersymmetry breaking.

Demonstrates moduli stabilization through fluxes and potential tuning at weak coupling.

Abstract

Nonlinear supersymmetry is used to compute the general form of the effective D-brane action in type I string theory compactified to four dimensions in the presence of internal magnetic fields. In particular, the scalar potential receives three contributions: (1) a nonlinear part of the D-auxiliary component, associated to the Dirac-Born-Infeld action; (2) a Fayet-Iliopoulos (FI) D-term with a moduli-dependent coefficient; (3) a D-auxiliary independent (but moduli dependent) piece from the D-brane tension. Minimization of this potential leads to three general classes of vacua with moduli stabilization: (i) supersymmetric vacua allowing in general FI terms to be cancelled by non-trivial vacuum expectation values (VEV's) of charged scalar fields; (ii) anti-de Sitter vacua of broken supersymmetry in the presence of a non-critical dilaton potential that can be tuned at arbitrarily weak string coupling; (iii) if the dilaton is fixed in a supersymmetric way by three-form fluxes and in the absence of charged scalar VEV's, one obtains non supersymmetric vacua with positive vacuum energy.