Energy Momentum Tensor of a Massless Scalar Quantum Field in a Robertson-Walker Universe

摘要: The renormalized stress tensor of a free quantum field in curved space-time should be obtainable by some covariant procedure from the short-distance behavior corresponding operator products evaluated at separated points. We perform expansion vacuum expectation value point-split conformally invariant scalar spatially flat Robertson-Walker geometry. When attempting to identify finite direction-independent part coincidence limit this quantity as tensor, we encounter ambiguities beyond those inevitable renormalizations coupling constants gravitational equations, but nevertheless limited local geometrical tensors fourth order or lower derivatives metric. are resolved requiring covariantly conserved and have trace form indicated recent research on conformal anomalies. Various techniques useful calculations kind described.