2025/09/17 by P. Diego-Palazuelos, E. Komatsu, Eiichiro Komatsu +2 · 2 voices · 7 citations
Physics and Astronomy · #COSMIC cancer database #Cosmic background radiation #Cosmic microwave background #Cosmology #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #Dark energy #Dark matter #Galaxies: Formation, Evolution, Phenomena #Observational cosmology #Photon #Polarization (electrochemistry) #Telescope #astro-ph.CO
paper · pdf · doi:10.48550/arxiv.2509.13654
published in arXiv (Cornell University) (Cornell University)
openalex publication_date 2025/09/17 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The polarized light of the cosmic microwave background is sensitive to new physics that violates parity symmetry. For example, the interaction of photons with the fields of elusive dark matter and dark energy could cause a uniform rotation of the plane of linear polarization across the sky, an effect known as cosmic birefringence. We extract the cosmological rotation angle, β, using Bayesian analysis of parity-violating correlations, EB and TB, of polarization data from the Atacama Cosmology Telescope (ACT) Data Release 6. We use prior probabilities for instrumental miscalibration angles derived from the optics model for the ACT telescope and instruments, and marginalize over a residual intensity-to-polarization leakage. We measure β= 0.215^∘± 0.074^∘ (68% confidence level), which excludes β=0 with a statistical significance of 2.9σ. Although there remain systematics in the ACT data that are not understood and do not allow us to draw strong cosmological conclusions, this result is consistent with previous independent results from the WMAP and Planck missions. It is suggestive that independent data sets and analyses using different methodologies have yielded the same sign and comparable magnitudes for β.