Anomalies & Tadpoles

TL;DR

This paper establishes a direct link between massless RR tadpoles in open and unoriented string theories and anomalies, providing a method to identify and parametrize anomalies via boundary reflection coefficients.

Contribution

It introduces a novel explicit parametrization of the anomaly polynomial using boundary reflection coefficients and relates RR tadpoles to anomalies in string theory.

Findings

RR tadpoles from sectors with non-zero Witten index correspond to irreducible anomalies

Anomalous amplitudes with more external legs reveal remaining RR tadpole anomalies

Boundary reflection coefficients parametrize the anomaly polynomial and help extract WZ couplings

Abstract

We show that massless RR tadpoles in vacuum configurations with open and unoriented strings are always related to anomalies. RR tadpoles arising from sectors of the internal SCFT with non-vanishing Witten index are in one-to-one correspondence with conventional irreducible anomalies. The anomalous content of the remaining RR tadpoles can be disclosed by considering anomalous amplitudes with higher numbers of external legs. We then provide an explicit parametrization of the anomaly polynomial in terms of the boundary reflection coefficients, i.e. one-point functions of massless RR fields on the disk. After factorization of the reducible anomaly, we extract the relevant WZ couplings in the effective lagrangians.