We show how discrete torsion can be implemented in D = 4, Script N = 1 type-IIB orientifolds. Some consistency conditions are found from the closed string and open string spectrum and from tadpole cancellation. Only real values of the discrete torsion parameter are allowed, i.e. epsilon = +/-1. Orientifold models are related to real projective representations. In a similar way as complex projective representations are classified by H2(Γ,Bbb C*) = H2(Γ,U(1)), real projective representations are characterized by H2(Γ,Bbb R*) = H2(Γ,Bbb Z2). Four different types of orientifold constructions are possible. We classify these models and give the spectrum and the tadpole cancellation conditions explicitely.
Journal of High Energy Physics
- Pub Date:
- July 2000
- High Energy Physics - Theory
- Latex, 48 pages, v2: several misprints and sign errors corrected, clarifications and references added