Proton Stability In Supersymmetric SU(5)
  Within supersymmetric SU(5) GUT we suggest mechanisms for suppression of baryon number violating dimension five and six operators. The mechanism is based on the idea of split multiplets (i.e. quarks and leptons are not coming from a single GUT state) which is realized by an extension with additional vector-like matter. The construction naturally avoids wrong asymptotic relation $\hat{M}_D=\hat{M}_E$. Thus, the long standing problems of the minimal SUSY SU(5) GUT can be resolved.   In a particular example of flavor structure and with additional ${\cal U}(1)\tm {\cal Z}_{3N}$ symmetry we demonstrate how the split multiplet mechanism works out. Namely, the considered model is compatible with successful gauge coupling unification and realistic fermion mass pattern. The nucleon decay rates are relatively suppressed and can be well compatible with current experimental bounds. 
Zurab Tavartkiladze