From Eduardo Fradkin
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Physics 582 (QFT I) Fall 2020 zoom lecture on Wednesday December 2, 2020. Today we discussed Feynman rules in momentum space and wrote the expressions for a few diagrams in 𝜙^4 theory. We also discussed briefly the Feynman rules for QED. We introduce the concept of one-particle irreducible diagrams and used it to define the self energy and the vertex functions. We defined the renormalized mass and coupling constant and compute it to one loop level. We discussed the application of the concepts to the theory of phase transitions. We also had a brief and qualitative discussion of the renormalization flow.