Constraining Ultralight ALP Dark Matter in Light of Cosmic Birefringence

Understand

Cosmic birefringence, the observed rotation of the polarization plane of the cosmic microwave background (CMB), serves as a compelling probe for parity-violating physics beyond the Standard Model.

• This study explores the potential of ultralight axion-like particle (ALP) dark matter to explain the observed cosmic birefringence in the CMB.
• We focus on the previously understudied mass range of $10^{-25}$ eV to $10^{-23}$ eV, where ALPs start to undergo nonlinear clustering in the late universe.
• Our analysis incorporates recent cosmological constraints and considers the washout effect on CMB polarization.