Two interacting scalar fields: practical renormalization

The main theme of the paper is the detailed discussion of the renormalization of the quantum field theory comprising two interacting scalar fields. The potential of the model is the fourth-order homogeneous polynomial of the fields, symmetric with respect to the transformation $\phi_{i}\rightarrow{-\phi_{i}}$. We determine the Feynman rules for the model and then we present a detailed discussion of the renormalization of the theory at one loop. Next, we derive the one loop renormalization group equations for the running masses and coupling constants. At the level of two loops, we use the FeynArts package of Mathematica to generate the two loops Feynman diagrams and calculate in detail the setting sun diagram.