Flavor changing nucleon decay

Recent discovery of neutrino large mixings implies the large mixings in the diagonalizing matrices of 5¯ fields in SU(5) grand unified theory (GUT), while the diagonalizing matrices of 10 fields of SU(5) are expected to have small mixings like Cabibbo-Kobayashi-Maskawa matrix. We calculate the predictions of flavor changing nucleon decays (FCND) in SU(5), SO(10), and E6 GUT models which have the above features for mixings. We found that FCND can be the main decay mode and play an important role to test GUT models.