Consequences of neutrinoless double beta decay and WMAP

Observation of the neutrinoless double beta decay (0nubetabeta) has established that there is lepton number violation in nature and the neutrino masses are Majorana in nature. It also gives the absolute mass of the neutrinos and discriminates between different models of neutrino masses. The allowed amount of lepton number violation puts severe constraints on some possible new physics beyond the standard model. The recent results from WMAP are consistent with the consequences of the neutrinoless double beta decay. They improve some of these constraints very marginally, which we shall summarize here. We mention the new physics which is not affected by WMAP, and which could make the limits from the neutrinoless double beta decay even consistent with much tighter future cosmological limits.