Superradiance in string theory

We perform an extensive analysis of the statistics of axion masses and interactions in compactifications of type IIB string theory, and we show that black hole superradiance excludes some regions of Calabi-Yau moduli space. Regardless of the cosmological model, a theory with an axion whose mass falls in a superradiant band can be probed by the measured properties of astrophysical black holes, unless the axion self-interaction is large enough to disrupt formation of a condensate. We study a large ensemble of compactifications on Calabi-Yau hypersurfaces, with 1 <= h(1,1) <= 491 closed string axions, and determine whether the superradiance conditions on the masses and self-interactions are fulfilled. The axion mass spectrum is largely determined by the Kahler parameters, for mild assumptions about the contributing instantons, and takes a nearly-universal form when h(1,1)>> 1. When the Kahler moduli are taken at the tip of the stretched Kahler cone, the fraction of geometries excluded initially grows with h(1,1), to a maximum of approximate to 0.5 at h(1,1) approximate to 160, and then falls for larger h(1,1). Further inside the Kahler cone, the superradiance constraints are far weaker, but for h(1,1)>> 100 the decay constants are so small that these geometries may be in tension with astrophysical bounds, depending on the realization of the Standard Model.

Automated summary

In this study, an extensive analysis of axion masses and interactions in compactifications of type IIB string theory was performed, revealing that black hole superradiance excludes certain regions of Calabi-Yau moduli space. The study shows that the properties of astrophysical black holes can probe theories with axion masses falling in a superradiant band, unless disrupted by large axion self-interactions. The mass spectrum of axions is largely determined by the Kahler parameters, with constraints on superradiance conditions varying depending on the value of h(1,1).