  We study numerically the problem of dynamical thermalization of interacting
cold fermionic atoms placed in an isolated Sinai-oscillator trap. This system
is characterized by a quantum chaos regime for one-particle dynamics. We show
that for a many-body system of cold atoms the interactions, with a strength
above a certain quantum chaos border given by the Aberg criterion, lead to the
Fermi-Dirac distribution and relaxation of many-body initial states to the
thermalized state in absence of any contact with a thermostate. We discuss the
properties of this dynamical thermalization and its links with the
Loschmidt-Boltzmann dispute.
