Cosmic birefringence from CP-violating axion interactions

• DOI: 10.1007/jhep08(2024)038
• Publication Date: 2024-08-12T12:02:32Z
• Authors: Xuheng Luo; Anubhav Mathur
• Keywords: CP violation

A bstract We explore the cosmic birefringence signal produced by an ultralight axion field with a small CP-violating coupling to bulk SM matter in addition usual CP-preserving photon coupling. The change vacuum expectation value of between recombination and today results frequency-independent rotation plane CMB linear polarization across entire sky. While many previous approaches rely on rolling from large initial value, couplings considered this work robustly generate regardless conditions, sourcing cosmological nucleon density. place bounds such monopole-dipole interactions using measurements angle Planck WMAP data, which improve upon existing constraints up three orders magnitude. also discuss UV completions model, possible strategies avoid fine-tuning mass.