The anomaly that was not meant IIB

TL;DR

This paper investigates quantum anomalies in the duality group of Type IIB supergravity, finds they do not vanish, and proposes mechanisms to cancel them, revealing new consistent theories with different extended object spectra.

Contribution

It explicitly computes the duality anomalies in Type IIB supergravity and introduces a novel anomaly cancellation mechanism involving a modified Chern-Simons term and topological Green-Schwarz analogs.

Findings

Anomalies in Type IIB duality group do not vanish without modification.

A specific field content allows a Chern-Simons term adjustment to cancel anomalies.

Alternative theories with different extended objects spectra are possible, potentially in the Swampland.

Abstract

Type IIB supergravity enjoys a discrete non-Abelian duality group, which has potential quantum anomalies. In this paper we explicitly compute these, and present the bordism group that controls them, modulo some physically motivated assumptions. Quite surprisingly, we find that they do not vanish, which naively would signal an inconsistency of F-theory. Remarkably, a subtle modification of the standard 10d Chern-Simons term cancels these anomalies, a fact which relies on the ***specific*** field content of type IIB supergravity. We also discover other ways to cancel this anomaly, via a topological analog of the Green-Schwarz mechanism. These alternative type IIB theories have the same low energy supergravity limit as ordinary type IIB, but a different spectrum of extended objects. They could either be part of the Swampland, or connect to the standard theory via domain walls.