Decoupling A and B model in open string theory -- Topological adventures in the world of tadpoles

Understand

In this paper we analyze the problem of tadpole cancellation in open topological strings.

• We prove that the inclusion of unorientable worldsheet diagrams guarantees a consistent decoupling of A and B model for open superstring amplitudes at all genera.
• This is proven by direct microscopic computation in Super Conformal Field Theory.
• For the B-model we explicitly calculate one loop amplitudes in terms of analytic Ray-Singer torsions of appropriate vector bundles and obtain that the decoupling corresponds to the cancellation of D-brane and orientifold charges.