Theoretical Physics Colloquium: Edward Hardy

Abstract: The QCD axion is among the best-motivated candidates for physics beyond the Standard Model, and it can also lead to a range of interesting cosmological and astrophysical effects if it comprises Dark Matter. I will discuss the so-called post-inflationary scenario, in which cosmic axion strings form at early times. In this case, the dark matter axions are produced with a non-trivial spatial distribution that leads to relatively dense substructure in the late Universe. I will argue that this substructure has several interesting, previously unconsidered, features, which might have observational or experimental implications.