Rigid D6-branes on T6/[Z(2)xZ(2M)xOmegaR] with discrete torsion

TL;DR

This paper classifies rigid D6-branes on specific orientifold backgrounds, analyzing supersymmetry, tadpole cancellation, and spectra, revealing new possibilities for Standard Model constructions and limitations on GUT models.

Contribution

It provides a comprehensive classification of rigid D6-branes on T6/[Z(2)xZ(2M)xOmegaR] orientifolds, including all spectra and conditions, with new examples and constraints for model building.

Findings

Existence of fully rigid D6-branes on Z(2)xZ(6) and Z(2)xZ(6') despite self-intersections.

Complete spectra and conditions for all inequivalent lattices with/without discrete torsion.

Constraints ruling out Standard and GUT models on Z(2)xZ(4).

Abstract

We give a complete classification of T6/[Z(2)xZ(2M)xOmegaR] orientifolds on factorisable tori and rigid D6-branes on them. The analysis includes the supersymmetry, RR tadpole cancellation and K-theory conditions and complete massless open and closed string spectrum (i.e. non-chiral as well as chiral) for fractional or rigid D6-branes for all inequivalent compactification lattices, without and with discrete torsion. We give examples for each orbifold background, which show that on Z(2)xZ(6) and Z(2)xZ(6') there exist completely rigid D6-branes despite the self-intersections of orbifold image cycles. This opens up a new avenue for improved Standard Model building. On the other hand, we show that Standard and GUT model building on the Z(2)xZ(4) background is ruled out by simple arguments.