According to the standard cosmology, near the last scattering surface, the photons scattered via Compton scattering are just linearly polarized and then the primordial circular polarization of the CMB photons is zero. In this work we show that CMB polarization acquires a small degree of circular polarization when a background magnetic field is considered or the quantum electrodynamic sector of standard model is extended by Lorentz-noninvariant operators as well as noncommutativity. The existence of circular polarization for the CMB radiation may be verified during future observation programs and it represents a possible new channel for investigating new physics effects.Comment: 28 pages, v3, Phys. Rev. D 81, 084035 (2010

Considering the effective Euler-Heisenberg Lagrangian, i.e., non-linear photonphoton interactions, we study the circular polarization of electromagnetic radiation based on the time-evolution of Stokes parameters. To the leading order, we solve the Quantum Boltzmann Equation for the density matrix describing an ensemble of photons in the space of energy-momentum and polarization states, and calculate the intensity of circular polarizations. Applying these results to a linear polarized thermal radiation, we calculate the circular polarization intensity, and discuss its possible relevance to the circular polarization intensity of the Cosmic Microwave Background radiation. : 73.50.Fq, 42.50.Xa, 98.70.Vc Introduction. Modern cosmological observations of the cosmic microwave background (CMB) radiation provide important evidences to understand our Universe. Cosmological informations encoded in the CMB radiation concerns not only temperature fluctuations and the spectrum of anisotropy pattern, but also the intensity and spectrum PACS

Standard cosmological models do predict a measurable amount of anisotropies in the intensity and linear polarization of the Cosmic Microwave Background radiation (CMB) via Thomson scattering, even though these theoretical models do not predict circular polarization for CMB radiation. In other hand, the circular polarization of CMB has not been excluded in observational evidences. Here we estimate the circular polarization power spectrum C V (S) l in CMB radiation due to Compton scattering and non-linear photon-photon forward scattering via Euler-Heisenberg Effective Lagrangian. We have estimated the average value of circular power spectrum is 1(l + 1) C V (S) l /(2π) ∼ 10 −4 µ K 2 for l ∼ 300 at present time which is smaller than recently reported data (SPIDER collaboration) but in the range of the future achievable experimental data. We also show that the generation of B-mode polarization for CMB photons in the presence of the primordial scalar perturbation via Euler-Heisenberg interaction is possible however this contribution for B-mode polarization is not remarkable.

To probe the nonlinear effects of photon-photon interaction in the quantum electrodynamics, we study the generation of circular polarized photons by the collision of two linearly polarized laser beams. In the framework of the Euler-Heisenberg effective Lagrangian and the Quantum Boltzmann equation for the time evolution of the density matrix of polarizations, we calculate the intensity of circular polarizations generated by the collision of two linearly polarized laser beams and estimate the rate of generation. As a result, we show that the generated circular polarization can be experimentally measured, on the basis of optical laser beams of average power KW, which are currently available in laboratories. Our study presents a valuable supplementary to other theoretical and experimental frameworks to study and measure the nonlinear effects of photon-photon interaction in the quantum electrodynamics.