From massive neutrinos and inos and the upper cut-off to the fractal structure of the Universe to recent progress in theoretical cosmology

摘要

We study pair plasma appioaching thermal equilibrium, starting from nonequilibrium configuration in the energy range 0.1-10MeV. In this energy range a number of important phenomena takes place during cosmological expansion, such as decoupling of neutrinos and the synthesis of the light elements. Dynamics of these phenomena is sensitive to the assumption of thermal equilibrium, adopted in relativistic cosmology. By numerical solution of relativistic Boltzmann equations we show that the plasma reaches thermal equilibrium on a short timescale tth < 10~12 s, which is much shorter than the expansion timescale tex = -ff(i)-1 at that moment. This result proves the assumption on thermal equilibrium in the above-mentioned energy range, thus confirming predictions of the standard cosmological model.