Vacuum Energy Decay
  The problem of the vacuum energy decay is studied through the analysis of the vacuum survival amplitude ${\mathcal A}(z, z')$. Transition amplitudes are computed for finite time-span, $Z\equiv z^\prime-z$, and their {\em late time} behavior is discussed up to first order in the coupling constant, $\l$. 
Enrique \'Alvarez, Roberto Vidal
hep-th