Two-point functions of Neumann-Dirichlet open-string sector moduli

Understand

We compute at one loop the two-point functions of massless scalars in the Neumann-Dirichlet open-string sector of the type IIB orientifold compactified on $T^2\times T^4/\mathbb{Z}_2$, when $\mathcal{N}=2$ supersymmetry is spontaneously broken.

• This is done by evaluating correlation functions of ``boundary-changing vertex operators'' which are analogous to correlators of twist fields for closed strings.
• We use our results to compute the mass developed at one loop by the moduli fields arising in the Neumann-Dirichlet sector.