Exact Results in Quantum Theory

I have been asked to present basic points of my full-semester lecture on effective quantum field theories in a couple of seminar talks. In the first talk, I am going to discuss the simplest examples, namely the Weak Effective Theory (WET) and the Heavy Quark Effective Theory (HQET). They will serve as a starting point for future discussion of Non-Relativistic QED and its application to evaluating the Lamb shift with the help of dimensional regularization.