Constraints on pseudoscalar-photon interaction from CMB polarization observation

Effective pseudoscalar-photon interaction(s) would induce a rotation of linear polarization of electromagnetic wave propagating with cosmological distance in various cosmological models. Pseudoscalar-photon interaction is proportional to the gradient of the pseudoscalar field. From phenomenological point of view, this gradient could be neutrino number asymmetry, other density current, or a constant vector. In these situations, Lorentz invariance or CPT may effectively be violated. CMB polarization observations are superb tests of these models and have the potential to discover new fundamental physics. In this paper, we review the constraints on pseudoscalar-photon interaction from CMB polarization observation.