Atlas of Fundamental Concepts

Begin with physical scale and interacting quantum fields. Perturbation theory introduces regularization and renormalization; running couplings encode scale dependence; the renormalization group and Wilsonian effective action turn this into a flow through theory space. Effective field theory then explains decoupling and controlled low-energy expansions, illustrated by QED, QCD, Fermi theory, chiral and nuclear EFT, SMEFT, and LEFT.