If neutrinos have nonzero rest masses, then, either in matter or in vacuum, a neutrino of one type can change into one of another. This phenomenon is known as neutrino oscillation. In the present theoretical physics project, an attempt will be made to achieve a more correct and thorough understanding of the behavior of massive neutrinos in matter and in vacuum, and in particular a better understanding of neutrino oscillation. Since the observation of neutrino oscillation, with its implication that neutrinos have mass, could be the first evidence for any physics beyond the well- established so-called "Standard Model" of the elementary particles and forces, a correct understanding of oscillation is very important.
