Perturbative Approach to Non-renormalizable Theories

On the perturbatively non-renormalizable and non-perturbatively finite examples (delta-function type potential in non-relativistic quantum mechanics and the mathematical model of the propagator by Redmond and Uretsky in quantum field theory) we illustrate that one can develop a perturbative approach for non-renormalizable theory. The key idea is the introduction of finite number of additional expansion parameters which allows us to eliminate all infinities from the perturbative expressions. The generated perturbative series reproduce the expansions of the exact analytical solutions.