Work

n π Phase Ambiguity of Cosmic Birefringence

Year: 2025

Type: article

Abstract: We point out that the rotation angle β of cosmic birefringence, which is a recently reported parity-violating signal in the cosmic microwave background (CMB), has a phase ambiguity of nπ(n∈Z). This ambiguity has a significant impact on the interpretation of the origin of cosmic birefringence. Assuming an axionlike particle (ALP) as the origin of cosmic birefringence, this ambiguity can be partly broken by the anisotropic cosmic birefringence and the shape of the CMB angular power spectra. We forecast constraints on n from ongoing and upcoming experiments and find that most nonzero values of n can be excluded using the cross-power spectrum between E and B modes. We also find that measuring the reionization bump in the E-mode auto-power spectrum can give further constraints, provided that the optical depth τ is determined independently of the CMB. The change in the low-l E-mode power spectrum may also provide a potential solution to the tension in τ suggested by the latest CMB and baryon acoustic oscillation measurements.

Source: Physical Review Letters

DOI: 10.1103/6z1m-r1j5

Authors: Fumihiro Naokawa, Toshiya Namikawa, Kai Murai, Ippei Obata, Kohei Kamada

Institutions: The University of Tokyo, Kavli Institute for the Physics and Mathematics of the Universe, Tohoku University, International Centre for Theoretical Physics Asia-Pacific, University of Chinese Academy of Sciences

Language: English

Topic: Cosmology and Gravitation Theories

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: green

Funders: National Energy Research Scientific Computing Center, Ministry of Education, Culture, Sports, Science and Technology, National Natural Science Foundation of China, Japan Society for the Promotion of Science