Contorted Flavors in Grand Unification and Proton Decay
  Conventionally we collect electron and up/down-quarks (u,d)+(nu_e,e) to form unified generations, and collect the left-handed and the right-handed fermions of the same flavors (nu_e,e)+e^c. We can alternatively have a contorted multiplet, made by pairing different quarks and leptons, like (u,d)+(nu_mu,mu) or (u,d)+(nu_tau,tau), and/or between different left and right handed fermions to (nu_e,e)+mu^c, etc. These can suppress proton decay, due to its high flavor dependence, while having the correct fermion masses. 
Kang-Sin Choi