Speaker
Masaki Yamada
(Tohoku University)
Description
Cosmic birefringence is predicted if an axion-like particle (ALP) moves after the recombination. We show that this naturally happens if the ALP is coupled to the dark matter density because it then acquires a large effective mass after the matter-radiation equality. We give a simple model to realize this scenario, where dark matter is made of hidden monopoles, which give the ALP such a large effective mass through the Witten effect. The mechanism works if the ALP decay constant is of order the GUT-scale without a fine-tuning of the initial misalignment angle.
Authors
Shota Nakagawa
(Tohoku University)
Fuminobu Takahashi
Masaki Yamada
(Tohoku University)
