Sigma-model symmetry in orientifold models

TL;DR

This paper examines sigma-model symmetry in Type IIB orientifold models, demonstrating anomaly cancellation via a Green-Schwarz mechanism involving twisted RR axions, thus supporting duality conjectures with heterotic orbifolds.

Contribution

It provides the first detailed computation of quantum anomalies in sigma-model symmetry for orientifold models and confirms their cancellation through a Green-Schwarz mechanism.

Findings

Anomalies are canceled via a Green-Schwarz mechanism.

The effective vertex operator matches a geometric deformation.

Complete anomaly polynomial is computed and shown to cancel.

Abstract

We investigate in the simplest compact D=4 N=1 Type IIB orientifold models the sigma-model symmetry suggested by the proposed duality of these models to heterotic orbifold vacua. This symmetry is known to be present at the classical level, and is associated to a composite connection involving untwisted moduli in the low-energy supergravity theory. In order to study possible anomalies arising at the quantum level, we compute potentially anomalous one-loop amplitudes involving gluons, gravitons and composite connections. We argue that the effective vertex operator associated to the composite connection has the same form as that for a geometric deformation of the orbifold. Assuming this, we are able to compute the complete anomaly polynomial, and find that all the anomalies are canceled through a Green-Schwarz mechanism mediated by twisted RR axions, as previously conjectured. Some questions about the field theory interpretation of our results remain open.