On general flux backgrounds with localized sources

TL;DR

This work develops a unified framework for localized Bianchi identities in string compactifications with RR, NSNS, and geometric fluxes and localized sources, showing that these constraints are tied by T- and S-dualities and share a common M-theory origin. It generalizes the Freed–Witten anomaly condition to include geometric fluxes and outlines new localized BIs involving NSNS sources and RR fluxes, establishing their role in preserving gauge invariance and axionic shift symmetries in the 4D effective action. The authors derive these constraints from 10D bulk BIs and from a detailed M-theory analysis of D6- and KK5-brane systems, including MMS-like instabilities and brane-ending–on–brane decay processes that allow interpolating domain walls between vacua. The results constrain consistent flux–brane configurations, inform the stability of non-supersymmetric vacua, and offer a framework to study landscape transitions, with potential extensions to non-trivial magnetic flux and more general duality webs.

Abstract

We derive new consistency conditions for string compactifications with generic fluxes (RR, NSNS, geometrical) and localized sources (D-branes, NS-branes, KK-monopoles). The constraints are all related by string dualities and share a common origin in M-theory. We also find new sources of instabilities. We discuss the importance of these conditions for the consistency of the effective action and for the study of interpolating solutions between vacua.