Vacuum polarization in curved backgrounds deduced from Hadamard kernels.

The point-splitting method of regularization is applied to alternative Hadamard kernels, for scalar fields in curved backgrounds, in order to study the polarization term in the vacuum expectation value (VEV) of the energy-momentum tensor. An ansatz to define this term is introduced and verified in several cases. The renormalized VEV of the energy-momentum tensor of a scalar massive conformally coupled field in a Robertson–Walker universe is explicitly computed. Two terms appear, the polarization term, which coincides with the one computed using the above-mentioned ansatz, and a creation of particle term. [ABSTRACT FROM AUTHOR]