Discrete torsion orbifolds and D-branes II

TL;DR

This paper investigates the consistency conditions for D-branes in orbifold theories with discrete torsion, revealing the necessity of both conventional and projective representations in the D-brane spectrum and uncovering novel non-BPS branes in certain orbifolds.

Contribution

It demonstrates the requirement of mixed D-brane representations for consistency in orbifolds with discrete torsion and generalizes the analysis to more complex orbifolds with new non-BPS brane phenomena.

Findings

D-brane spectra include both conventional and projective representations.

In C^3/Z_N x Z_N orbifolds, non-BPS branes charged under twisted R-R potentials are found.

Consistency conditions impose specific representation structures on D-branes.

Abstract

The consistency of the orbifold action on open strings between D-branes in orbifold theories with and without discrete torsion is analysed carefully. For the example of the C^3/Z_2 x Z_2 theory, it is found that the consistency of the orbifold action requires that the D-brane spectrum contains branes that give rise to a conventional representation of the orbifold group as well as branes for which the representation is projective. It is also shown how the results generalise to the orbifolds C^3/Z_N x Z_N for which a number of novel features arise. In particular, the N>2 theories with minimal discrete torsion have non-BPS branes charged under twisted R-R potentials that couple to none of the (known) BPS branes.