Speaker
Description
We study axion-photon couplings in compactifications of type IIB string theory.
We find that these couplings are systematically suppressed compared to the inverse axion periodicity, as a result of two effects. First, couplings to the QED theta angle are suppressed for axion mass eigenstates that are light compared to the mass scale set by stringy instantons on the cycle supporting QED. Second, in compactifications with many axions the intersection matrix is sparse, making kinetic mixing weak. We study the resulting phenomenology in an ensemble of explicit models constructed from the Kreuzer-Skarke database up to the maximum number of axions, 491. We also explore the general features of this axiverse and give a simple geometric model for some of its properties.
