Quantum Boltzmann Equations in the Early Universe

Abstract

Physics of the early universe unavoidably falls into the domain of quantum dynamics far from thermal equilibrium. Since properties of specific theories, like leptogenesis or preheating, are to be tested experimentally in the near future, it is important to assess the validity of (semi-)classical or Boltzmann-type approximations underlying their predictions. A complete quantum-mechanical description of nonequilibrium processes is furnished by so-called Kadanoff-Baym equations, which are quantum mechanical generalizations of classical Boltzmann equations. Kadanoff-Baym equations take memory effects into account, which is reflected by their non-Markovian structure.