Denmark in the same year. One year later, he received his PhD at the Niels Bohr Institute in Copenhagen. He then worked as a post-doctoral fellow at the Niels Bohr Institute until 1975.

After a fellowship in the CERN theory group from 1975 to 1977, he was first a visitor and then a staff member in the Fermilab theory group from 1977 till 1982. He then became staff member of the Max Planck Institute for Physics