Physics 583 (QFT II) Spring 2921 zoom lecture on Tuesday March 16, 2021. Today we calculated the OPE for 𝜙^4  theory around the free massless fixed point and used conformal perturbation theory to compute the beta functions and identify the fixed points. In the 2nd part of the lecture we returned to renormalized perturbation theory and used it to derive the Callan-Symanzik equations. We solved these equations by introducing a flow in momentum scales and in the coupling constants.