Type-I strings on magnetised orbifolds and brane transmutation

TL;DR

This paper explores how internal magnetic fields on D-branes in string theory can lead to new supersymmetric vacua with reduced gauge groups, involving brane transmutation and novel Green-Schwarz couplings.

Contribution

It introduces self-dual magnetic field configurations on D-branes that produce supersymmetric vacua with reduced gauge groups and unique R-R couplings, expanding the understanding of brane dynamics.

Findings

Self-dual magnetic fields can produce supersymmetric vacua.

Magnetic energy can offset negative tensions of orientifold planes.

New Green-Schwarz couplings to untwisted R-R forms are identified.

Abstract

In the presence of internal magnetic fields, a D9 brane can acquire a D5 (or anti-D5) R-R charge, and can therefore contribute to the corresponding tadpole. In the resulting vacua, supersymmetry is generically broken and tachyonic instabilities are present. However, suitable choices for the magnetic fields, corresponding to self-dual configurations in the internal space, can yield new chiral supersymmetric vacua with gauge groups of reduced rank, where the magnetic energy saturates, partly or fully, the negative tension of the O5+ planes. These models contain Green-Schwarz couplings to untwisted R-R forms not present in conventional orientifolds.