Finite temperature quantum field theory on non compact domains and application to delta interactionsinteractions in three dimensions

We use relative zeta functions technique of W. Muller \cite{Mul} to extend the classical decomposition of the zeta regularized partition function of a finite temperature quantum field theory on a ultrastatic space-time with compact spatial section to the case of non compact spatial section. As an application, we study the case of Schr\"odinger operators with delta like potential, as described by Albeverio & alt. in \cite{AGHH}.