Regularization of Vacuum Fluctuations and Frame Dependence
  We discuss the regularization of vacuum fluctuations in a gravitational background. It is shown that general covariance is broken even by a 4-momentum cut-off, consistent with Lorentzian symmetry. It is pointed out that general covariance is a protective symmetry for the vacuum energy from power divergences. 
Juri Smirnov
hep-th gr-qc hep-ph