Prof. Dr. Walter Dittrich was head of the quantum electrodynamics group at Tübingen University. His main research activities centered on gauge theories, in particular, on QED, stimulated in part by collaboration with Julian Schwinger. Walter Dittrich has worked for more than 20 years at centers like MIT, the Institute for Advanced Study at Princeton and the National Accelerator Laboratory at Stanford (SLAC). He has over 30 years of teaching experience and is one of the key scientists in developing the theoretical framework of quantum electrodynamics.   Prof. Dr. Martin Reuter is head of the quantum Einstein gravity group at the Institute for High Energy Physics at Mainz University. His research focuses on particle physics, quantum field theory and quantum Einstein gravity. He worked at the synchrotron facility DESY and the large hadron collider at CERN. He has more than 30 years of teaching experience in theoretical physics.