In the present lectures the following topics are considered: general properties of neutrinos, neutrino mass phenomenology (Dirac and Majorana masses), neutrino masses in the simplest extensions of the standard model (including the seesaw mechanism), neutrino oscillations in vacuum, neutrino oscillations in matter (the MSW effect) in 2-and 3-flavour schemes, implications of CP, T and CPT symmetr...

The program of reconstruction of the neutrino mass and flavor spectrum is outlined and the present status of research is summarized. We describe the role of future solar and atmospheric neutrino experiments, detection of the Galactic supernovae and double beta decay searches in accomplishing this program. The LSND result and four neutrino mass spectra are considered in connection with recent se...

We show that the Fritzsch texture of lepton mass matrices can naturally lead to the bi-large flavor mixing pattern, if three neutrinos have a normal but weak mass hierarchy (typically, m1 : m2 : m3 ∼ 1 : 3 : 10). The effective mass of the tritium beta decay and that of the neutrinoless double beta decay are too small to be observable in this ansatz, but CP violation at the percent level is allo...

Recently the evidence of the neutrinoless double β (0νββ) decay has been announced. This means that neutrinos are Majorana particles and their mass hierarchy is forced to inverted mass hierarchy (Type B) or degenerate mass (Type C) patterns in the diagonal basis of charged lepton mass matrix. We estimate the magnitude of 0νββ decay in the degenerate neutrinos including the cosmological constrai...

We discuss four approaches to the determination of absolute neutrino mass. These are the measurement of the zero-neutrino double beta decay rate, of the tritium decay end-point spectrum, of the cosmic ray spectrum above the GZK cutoff, and the cosmological measurement of the power spectrum governing the CMB and large scale structure. The first two approaches are sensitive to the mass eigenstate...

We show that the bimaximal neutrino mixing pattern suggested by the solar and atmospheric neutrino data can be derived from the maximal, symmetric , four neutrino mixing in the limit that one of the neutrinos is made heavy. Imposing the constraints of no neutrinoless double beta decay and a 20% hot dark matter component of the universe leads to a three neutrino mass matrix recently suggested by...