Type I vacua with brane supersymmetry breaking

TL;DR

The paper addresses how to obtain consistent Type I vacua when $RR$ tadpoles obstruct supersymmetric brane configurations by introducing antibranes with non-supersymmetric worldvolumes, yielding tachyon-free spectra with bulk SUSY preserved and SUSY broken on branes. It analyzes explicit constructions, including $Z_2 imes Z_2$ orientifolds with discrete torsion, open descendants of $T^6/Z_4$, and toroidal compactifications with brane–antibrane pairs, showing how NS-NS tadpoles generate a scalar potential that can stabilize some internal radii. The results demonstrate that brane supersymmetry breaking can be realized in a controlled, tree-level framework where the breaking is tied to string-scale consistency conditions, and that the spectrum can be made chiral and anomaly-free through careful brane configurations. While this setup offers a route to phenomenologically interesting scenarios (e.g., low string scale or mediation from bulk SUSY), it does not resolve the four-dimensional cosmological constant problem and leaves a run-away dilaton in many cases.

Abstract

We show how chiral type I models whose tadpole conditions have no supersymmetric solution can be consistently defined introducing antibranes with non-supersymmetric world volumes. At tree level, the resulting stable non-BPS configurations correspond to tachyon-free spectra, where supersymmetry is broken at the string scale on some (anti)branes but is exact in the bulk, and can be further deformed by the addition of brane-antibrane pairs of the same type. As a result, a scalar potential is generated, that can stabilize some radii of the compact space. This setting has the novel virtue of linking supersymmetry breaking to the consistency requirements of an underlying fundamental theory.