  Nonequilibrium dynamics of an N-fold spin-degenerate ultracold Fermi gas is
described in terms of beyond-mean-field Kadanoff-Baym equations for correlation
functions. Using a nonperturbative expansion in powers of 1/N, the equations
are derived from the two-particle irreducible effective action in
Schwinger-Keldysh formulation. The definition of the nonperturbative
approximation on the level of the effective action ensures vital conservation
laws as, e.g., for the total energy and particle number. As an example, the
long-time evolution of a homogeneous, twofold spin-degenerate Fermi gas is
studied in one spatial dimension after an initial preparation far from thermal
equilibrium. Analysis of the fluctuation-dissipation relation shows that, at
low energies, the gas does not thermalise.
