Remarks on Global Anomalies in RCFT Orientifolds

TL;DR

The paper investigates potential global anomalies in RCFT orientifold constructions for supersymmetric standard-model spectra, even when tadpole cancellation holds. It applies Uranga's probe-brane criterion across a large RCFT-based spectrum database to derive parity (mod-2) constraints on CP multiplicities. The findings show global-anomaly constraints are relatively rare and rarely prune viable tadpole solutions, with a small set of MIPFs affected and a substantial, robust set of anomaly-free spectra confirmed on reanalysis. This supports the consistency and viability of RCFT orientifold spectra while underscoring the need for a first-principles derivation of global anomaly conditions and their relation to K-theory charges in these setups.

Abstract

We check the list of supersymmetric standard model orientifold spectra of Dijkstra, Huiszoon and Schellekens for the presence of global anomalies, using probe branes. Absence of global anomalies is found to impose strong constraints, but in nearly all cases they are automatically satisfied by the solutions to the tadpole cancellation conditions.