The recent discovery of neutrino masses has initiated a revolution in particle physics: the Standard Model, which survived all experimental tests for more than thirty years and describes physics starting from picoseconds after the big bang, has to be extended. My major aim of research is the theoretical and phenomenological investigation of neutrino masses and what they teach us about lepton number violation and physics beyond the Standard Model. These topics may well be one of the keys towards the old physicists dream to describe all phenomena in Nature in terms of a fundamental theory of everything or almost everything, namely superstring theories, implementing extra space dimensions and supersymmetry (SUSY) and grand unified theories (GUTs).

In the present decade, neutrino oscillation physics finally evolves into the stage of precision physics at terrestrial long baseline experiments. These efforts will be complemented by a flood of experimental data anticipated from cosmology, collider processes (the LHC will be switched on this year!), searches for rare particle decays and cosmic ray experiments. This development provides the fascinating possibility to test concrete models of neutrino mass generation linked to new physics beyond the reach of direct production experiments at accelerators. It also constitutes a challenge for theoretical physics to support the experimental efforts to reconstruct the neutrino mass matrix and to analyze what information about concrete scenarios of the new physics ahead is provided by the discoveries in neutrino physics.

Typical questions addressed by my work are: