Cosmological CPT violating effect on CMB polarization

A dark energy scalar (or a function of the Ricci scalar) coupled with the derivative to the matter fields will violate the $CPT$ symmetry during the expansion of the Universe. This type of cosmological $CPT$ violation helps to generate the baryon number asymmetry and gives rise to the rotation of the photon polarization which can be measured in the astrophysical and cosmological observations, especially the experiments of the cosmic microwave background radiation. In this paper, we derive the rotation angle in a fully general relativistic way and present the rotation formulas used for the cosmic microwave background data analysis. Our formulas include the corrections from the spatial fluctuations of the scalar field. We also estimate the magnitude of these corrections in a class of dynamical dark energy models for quintessential baryo/leptogenesis.Comment: 12 page

Cosmological CPT Violation, Baryon/Leptogenesis and CMB Polarization

In this paper we study the cosmological CPT-violation and its implications in baryo/leptogenesis and CMB polarization. We propose specifically a variant of the models of gravitational leptogenesis. By performing a global analysis with the Markov Chain Monte Carlo (MCMC) method, we find the current CMB polarization observations from the three-year WMAP (WMAP3) and the 2003 flight of BOOMERANG (B03) data provide a weak evidence for our model. However to verify and especially exclude this type of mechanism for baryo/leptogenesis with cosmological CPT-violation, the future measurements on CMB polarization from PLANCK and CMBpol are necessary.Comment: The version appears in PL

Primordial Gravitational Waves Measurements and Anisotropies of CMB Polarization Rotation

Searching for the signal of primordial gravitational waves in the B-modes (BB) power spectrum is one of the key scientific aims of the cosmic microwave background (CMB) polarization experiments. However, this could be easily contaminated by several foreground issues, such as the thermal dust emission. In this paper we study another mechanism, the cosmic birefringence, which can be introduced by a CPT-violating interaction between CMB photons and an external scalar field. Such kind of interaction could give rise to the rotation of the linear polarization state of CMB photons, and consequently induce the CMB BB power spectrum, which could mimic the signal of primordial gravitational waves at large scales. With the recent polarization data of BICEP2 and the joint analysis data of BICEP2/Keck Array and Planck, we perform a global fitting analysis on constraining the tensor-to-scalar ratio $r$ by considering the polarization rotation angle which can be separated into a background isotropic part and a small anisotropic part. Since the data of BICEP2 and Keck Array experiments have already been corrected by using the "self-calibration" method, here we mainly focus on the effects from the anisotropies of CMB polarization rotation angle. We find that including the anisotropies in the analysis could slightly weaken the constraints on $r$, when using current CMB polarization measurements. We also simulate the mock CMB data with the BICEP3-like sensitivity. Very interestingly, we find that if the effects of the anisotropic polarization rotation angle can not be taken into account properly in the analysis, the constraints on $r$ will be dramatically biased. This implies that we need to break the degeneracy between the anisotropies of the CMB polarization rotation angle and the CMB primordial tensor perturbations, in order to measure the signal of primordial gravitational waves accurately.Comment: 7 pages, 5 figure