Loop corrections and the K-matrix formalism

We propose a new model that combines the rigor of full-fledged loop calculations in field theory with the simplicity of the K-matrix formalism for channel-coupling effects. We show, for one example, the equivalence of this new model, the renormalized Im-K-matrix (RIK) model, with a more standard approach in which nonperturbative loop corrections are calculated. In the RIK model an analytic continuation of the K-matrix formalism is combined with a renormalization procedure to arrive at a scattering amplitude that obeys low-energy theorems and is also an analytic function in the complex momentum plane.