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T: Fachverband Teilchenphysik

T 8: Eingeladene Vorträge 3

T 8.1: Eingeladener Vortrag

Thursday, March 1, 2012, 14:00–14:30, ZHG 011

Baryon asymmetry of the Universe: a non-equilibrium QFT approach — •Alexander Kartavtsev — MPIK, Heidelberg

Today the observed universe almost entirely consists of matter, i.e. is baryonically asymmetric. A very attractive explanation of the observed asymmetry is provided by the baryogenesis via leptogenesis scenario. According to this scenario the excess of matter over antimatter has been generated by the CP-violating decay of heavy Majorana neutrinos.

CP-violation is an inherently quantum phenomenon. In the hot and expanding early Universe this as well as other quantum phenomena affecting the asymmetry generation can be studied using methods of non-equilibrium quantum field theory.

Applying these methods to the Standard Model supplemented by three right-handed neutrinos we find that the medium effects enhance the CP-violating parameter and, to a lesser extent, the total decay width. The medium effects also modify the scattering rates.

From theoretical and phenomenological point of view particularly interesting is the regime of resonant leptogenesis. It is realized for quasidegenerate mass spectrum of the Majorana neutrinos. In this regime we find considerable deviations from results of the canonical analysis. In the maximal resonant regime the usual Boltzmann picture breaks down and the oscillation effects start to play an important role.