to neutrino masses. These interactions are normally excluded from theories as they come from a class of interactions that lead to unacceptably rapid proton decay if they are all included. These models have little predictive power and are not able to provide a cold dark matter candidate. Oscillations in the early universe During the early universe when particle concentrations and temperatures were high, neutrino oscillations could have behaved differently. Depending on neutrino mixing-angle parameters and masses, a broad spectrum of behavior may arise including vacuum-like neutrino oscillations, smooth evolution, or self-maintained coherence. The physics for this system is non-trivial and involves neutrino oscillations in a dense neutrino gas. See also MSW effect Majoron Neutral kaon mixing Neutral particle oscillation Neutrino astronomy Notes References Further reading External links Review Articles on arxiv.org Ganesan Srinivasan was elected in 1984 a fellow of the Indian Academy of Sciences. Neutrinos Standard Model Electroweak theory Physics beyond the Standard Model