Renormalized stress tensor for trans-Planckian cosmology

Finite expressions for the mean value of the stress tensor corresponding to a scalar field with a generalized dispersion relation in a Friedmann-Robertson-Walker universe are obtained using adiabatic renormalization. Formally divergent integrals are evaluated by means of dimensional regularization. The renormalization procedure is shown to be equivalent to a redefinition of the cosmological constant and the Newton constant in the semiclassical Einstein equations.