Inhomogeneous lepton asymmetry and generation of cosmic magnetic fields and gravitational waves

by Alexander DOLGOV (INFN Ferrara & ITEP Moscow)

Thursday 23 Aug 2001, 14:00 → 15:00 Europe/Zurich

TH Auditorium (CERN)

Large scale cosmic magnetic fields present an unsolved cosmological mystery. Possible models of their generation usually involve physics at inflationary stage or high temperature phase transitions in the early universe. We propose a model for generation of astronomically large magnetic fields during the epoch of big bang nucleosynthesis (BBN). If there exists a sterile neutrino mixed with active ones, then neutrino oscillations in the cosmological background could give rise to a lepton asymmetry of order unity in the sector of active neutrinos. It can be shown that this asymmetry should be strongly inhomegeneous at (super)horizon scale during BBN. Resulting neutrino diffusion creates vorticity in usual matter and in turn sufficiently strong and long-wave magnetic fields. The same mechanism could lead to the generation of gravitational waves observable in future detectors.