Discrete torsion defects

Understand

Orbifolding two-dimensional quantum field theories by a symmetry group can involve a choice of discrete torsion.

• We apply the general formalism of `orbifolding defects' to study and elucidate discrete torsion for topological field theories.
• In the case of Landau-Ginzburg models only the bulk sector had been studied previously, and we re-derive all known results.
• We also introduce the notion of `projective matrix factorisations', show how they naturally describe boundary and defect sectors, and we further illustrate the efficiency of the defect-based approach by explicitly computing RR charges.