Flavor changing nucleon decay

Recent discovery of neutrino large mixings implies the large mixings in the diagonalizing matrices of $\bf\bar 5$ fields in $SU(5)$ grand unified theory (GUT), while the diagonalizing matrices of $\bf 10$ 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 $E_6$ GUT models which have the above features for mixings. We found that FCND can be the main decay mode especially for GUT with higher rank unification group. Recent report for $P\rightarrow \pi^0\mu^+$ process implies $E_6$ or $SO(10)$ GUT if the signal is from the nucleon decay.