Fuzzy Dark Matter from Clockwork Axion Model

Abstract

We consider in the clockwork axion model the realization of an ultralight axion which can serve as a fuzzy dark matter candidate. With the mixing terms between adjacent axions, the shift symmetries are broken except for one, which is responsible for the ultralight axion and its mass can be as light as 10−21 eV. This ultralight axion can satisfy easily the observed dark matter abundance and the isocurvature bound. The heavier axions resulting from the clockwork gears quickly decay before the big bang nucleosynthesis. © 2020, The Korean Physical Society.