Generation of circular polarization of gamma ray bursts

Abstract: The generation of the circular polarization of Gamma Ray Burst (GRB) photons is discussed in this paper via their interactions with astroparticles in the presence or absence of background fields such as magnetic fields and non-commutative space time geometry. Solving quantum Boltzmann equation for GRB-photons as a photon ensemble, we discuss the generation of circular polarization (as Faraday conversion phase shift $\Delta \phi_{FC}$) of GRBs in the following cases: (i) intermediate interactions, i.e. the Compton scattering of GRBs in the galaxy cluster magnetic field and in the presence of non-commutative space time geometry, as well as the scattering of GRBs in cosmic neutrino background (CNB), and in cosmic microwave background (CMB); (ii) interactions with particles and fields in shock wave, i.e. the Compton scattering of GRBs with accelerated charged particles in the presence of magnetic fields. We found that (i) after shock wave crossing, the most contribution of $\Delta \phi_{FC}$ for energetic GRBs (in order GeV and larger) comes from GRB-CMB interactions, however for low energy GRBs the contributions of the Compton scattering of GRBs in the galaxy cluster magnetic field dominate; (ii) in shock wave crossing, the magnetic filed has significant effects on converting GRB's linear polarization to circular one, this effect can be used to better understanding magnetic profile in shock wave. The main aim of this work is a emphasis that the studying and measuring the circular polarization of GRBs are helpful for better understanding of physics and mechanism of the generation of GRBs and their interactions before reaching us.