Time evolution of T_{\mu\nu} and the cosmological constant problem
  We study the cosmic time evolution of an effective quantum field theory
energy-momentum tensor T_{\mu\nu} and show that, as a consequence of the
effective nature of the theory, the structure of T_{\mu\nu} is such that the
vacuum energy decreases with time. We find that the zero point energy at
present time is washed out by the cosmological evolution. The implications of
this finding for the cosmological constant problem are investigated.
