Rutgers University Department of Physics and Astronomy

Katie Fraser
(Harvard)

Title: Axion Interactions with Topological Defects

Abstract: Given that axions are both a promising candidate to solve problems in the Standard Model and are ubiquitous in quantum gravity, it is crucial to accurately determine their experimental signatures, in particular the effect of axion interactions with topological defects. In this talk, we discuss the interaction of axions with magnetic monopoles and the interaction of fermions with axion strings. In the case of monopoles, we show that when axions interact with abelian gauge fields, the Witten effect generates a potential from loops of magnetic monopoles that has previously been neglected, and discuss a simple phenomenological example where this can be the dominant effect. In the case of strings, we discuss superconductivity from massless chiral excitations along the string. Specifically, we show that bulk fermions do not need to become massless in the core of the string for there to be trapped massless excitations, contrary to common intuition. Counterintuitively, these zero modes become less and less localized to the string as the mass is increased, up until a critical value in which case these modes disappear.

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