Internal magnetic fields and supersymmetry in orientifolds

TL;DR

This paper explores the relationship between magnetic fluxes and supersymmetry in type I string orientifolds, introducing new supersymmetric models with magnetic fluxes and analyzing their spectra and tadpole conditions.

Contribution

It constructs new supersymmetric orientifold models with magnetic fluxes and investigates their tadpole cancellation and spectrum properties.

Findings

Equivalence between BPS D9 branes with fluxes and non-BPS D3 branes with inverted fluxes.

New supersymmetric Z_2 x Z_2 orientifolds with discrete torsion.

A nine-dimensional orientifold with Scherk-Schwarz deformation and non-BPS O9 planes.

Abstract

Within the context of type I strings, we show the equivalence between BPS D9 branes with internal magnetic fluxes H_i in the three torii and non-BPS D3 branes with inverted internal magnetic fluxes 1/H_i. We then construct new supersymmetric examples of Z_2 x Z_2 orientifolds with discrete torsion which in the past had only non-supersymmetric solutions and emphasize the role of new twisted tadpole cancellation conditions, arising in the presence of magnetic fields, in order to get a consistent spectrum. In a second and independent part of the paper, we construct a new nine-dimensional type IIB orientifold with Scherk-Schwarz deformation which has the peculiarity of introducing a new type of non-BPS O9 planes and which contains as top branes a Scherk-Schwarz deformation of non-BPS D9 branes.The model contains charged D7 and D3 branes with a soft supersymmetry breaking spectrum.