Neutrinoless double beta decay and new physics in the neutrino sector

Neutrinoless double beta decay belongs to the most sensitive tools for the search of new physics beyond the standard model. The recent half life limit of the Heidelberg-Moscow experiment implies restrictive bounds on the absolute mass scale in the neutrino sector. Possible improvements by the GENIUS project provide a unique possibility to reconstruct the neutrino mass spectrum. Further constraints on new interactions in the neutrino sector are given in a model-independent way. Consequences for neutrino anomalies and theories beyond the standard model such as left-right symmetric models, R-parity violating SUSY and leptoquarks are discussed. The potential of double beta decay experiments in the search for WIMP dark matter is reviewed.