“Krein” regularization method

The "Krein" regularization method of quantum field theory is studied, inspired by the Krein space quantization and metric fluctuations. It was previously considered in one-loop approximation, this paper generalized to all orders perturbation theory. We directly recover physical results obtained starting from standard QFT imposing renormalization conditions. By applying our approach curved space-time linear gravity, we discuss that there no need for higher derivative tensor advantage compared previous ones gravity renormalizable