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.
Bibliographical noteFunding Information:
This work was supported by the National Research Foundation of Korea grants funded by the Korean Government, 2020R1C1C1012452 (KJB) and 2019R1A2C2085023 (JG). JG also acknowledges the Korea-Japan Basic Scientific Cooperation Program supported by the National Research Foundation of Korea and the Japan Society for the Promotion of Science (2020K2A9A2A08000097) and the Ewha Womans University Research Grant of 2020 (1-2020-1630-001-1). JG is grateful to the Asia Pacific Center for Theoretical Physics for hospitality while this work was under progress.
© 2020, The Korean Physical Society.
- Dark matter
- Fuzzy dark matter