Speakers
Description
In this talk I will consider the string theory axiverse in type IIB Calabi-Yau orientifold compactifications, and focus on the computation of axion photon couplings and hierarchies that arise in the many axion limit — i.e. at large values of $h^{1,1}$. In particular, I will discuss two distinct phenomena that hierarchically suppress axion photon interactions when the QED divisor is small: the former is a suppression in ratios of mass scales that decouples all axions lighter than the QED axion. The latter is geometric in origin: at most a handful of mass eigenstates have internal wavefunctions that significantly overlap with QED.
Equipped with these insights I will present preliminary data on cosmic birefringence, and astrophysical constraints on the axiverse.
