Non-supersymmetric Orientifolds with D-branes at Angles
Gabriele Honecker
TL;DR
This work addresses the challenge of obtaining non-supersymmetric, chiral string vacua in type II orientifolds by employing branes at angles. It analyzes two constructions on $T^2\times (T^2)^2/Z_3$: D6-branes at angles and D8-branes, each with distinct RR-tadpole cancellation conditions and spectra, including Green-Schwarz anomaly cancellation mechanisms. Chiral matter arises at brane intersections with Yukawa hierarchies set by worldsheet areas $Y_{ijk}\sim e^{-A_{ijk}}$, and the setups admit tachyonic modes at intersections that may influence symmetry breaking. The paper demonstrates explicit tadpole-consistent spectra, discusses large-volume compactifications to lower the string scale, and highlights the potential for three-generation realizations, contributing a concrete framework for semi-realistic, non-supersymmetric string vacua with geometric control over couplings and scales.
Abstract
We present special classes of orientifold models involving supersymmetry breaking via branes at angles. Type II superstring theories are compactified on a two torus times a four-dimensional orbifold. Combining worldsheet parity with a reflection of half of the compact coordinates leads to D6-branes at angles which are mapped onto each other by the orbifold group, while applying the geometric action only along one coordinate leads to intersecting D8-branes with non-trivial transformation properties under the orbifold group. The models differ in the gauge groups and matter content.