A comment on discrete Kalb-Ramond field on orientifold and rank reduction

TL;DR

This paper explains how discrete Kalb-Ramond fields influence gauge group rank reduction on orientifolds through induced field strengths, affecting brane configurations and tadpole cancellation.

Contribution

It provides a new interpretation of rank reduction via induced field strengths in non trivial bundles, clarifying the role of discrete Kalb-Ramond fields in orientifold models.

Findings

Rank reduction is explained by induced field strengths.

Number of branes remains unchanged despite the background.

Discrete Kalb-Ramond fields are crucial for tadpole cancellation.

Abstract

We show that the rank reduction of the gauge group on orientifolds in presence of non vanishing discrete Kalb-Ramond field can be explained by the presence of an induced field strength in a non trivial bundle on the branes. This field strength is also necessary for the tadpole cancellation and the number of branes is left unchanged by the presence of the discrete Kalb-Ramond background.