Paul Hoyer is Professor Emeritus of particle physics at the University of Helsinki, where he received his Ph.D. in theoretical physics in 1973. During his career, he worked at CERN (Switzerland), the University of Oxford (UK), Stony Brook University, the Lawrence Berkeley National Laboratory (USA), and at the Nordic Institute for Theoretical Physics (NORDITA) in Copenhagen (Denmark). During his tenure at Helsinki University from 1981, he served as Director of NORDITA in Copenhagen 1994-2002. He has been a member and chair of the Board of the European Centre ECT* in Trento (Italy) and of the CP3-Origins Centre at the University of Southern Denmark. He has served on the Executive Committee of the European Physical Society and as a chair of the PANDA Experiment Theory Advisory Group at FAIR (Germany). His research has focused on the strong interactions, striving to describe data and explain phenomenology in terms of the underlying theory of quantum chromodynamics.

Motivations and Outline.- Brief survey of present QED approaches to atoms.- Dirac bound states.- Fock expansion of bound states in temporal (A⁰ = 0) gauge.- Applications to Positronium atoms.- QED in D = 1+1 dimensions.- Applications to QCD bound states.- Bound state epilogue.- Appendix: Solutions to exercises.