Cosmic Birefringence Triggered by Dark Matter Domination.

Area of Science:

• Cosmology
• Particle Physics
• Astrophysics

Background:

• Cosmic birefringence is a phenomenon where the polarization of light rotates as it travels through space.
• Axionlike particles (ALPs) are hypothetical particles that could be candidates for dark matter.
• The behavior of ALPs after cosmic recombination is crucial for understanding cosmic birefringence.

Purpose of the Study:

• To propose a mechanism for cosmic birefringence linked to axionlike particles (ALPs).
• To investigate how ALPs acquire mass and influence cosmic birefringence through interaction with dark matter.
• To explore implications for dark matter models and the QCD axion.

Main Methods:

• Developing a theoretical scenario where ALPs couple to dark matter density.
• Introducing a model with hidden monopoles as dark matter, inducing an effective mass in ALPs via the Witten effect.
• Analyzing the mass range for ALPs and conditions for the mechanism to operate.

Main Results:

• ALPs naturally acquire a large effective mass after matter-radiation equality when coupled to dark matter.
• This mechanism is effective for a wide range of ALP masses, including very low values (m_{ϕ}≲10^{-28} eV).
• The proposed model, utilizing hidden monopoles, can explain cosmic birefringence without fine-tuning the ALP decay constant.

Conclusions:

• The interaction between ALPs and dark matter provides a natural explanation for cosmic birefringence.
• The model offers a solution to the QCD axion domain wall problem.
• This research opens new avenues for probing dark matter and fundamental physics through cosmological observations.