He has during his career worked at Nordic Institute for Theoretical Physics (Denmark), Brookhaven National Laboratory (USA), CERN (Switzerland), og Institut des Hautes Études Scientifiques (France).
Har gennem sin karriere arbejdet ved Nordisk Institut for Teoretisk Fysik (Danmark), Brookhaven National Laboratory (USA), CERN(Schweiz), og Institut des hautes Etudes Scientifiques (Frankrig).