On the effective lagrangian for baryon decay

We discuss the flavour structure and short-distance renomalization of the effective lagrangian for baryon decay. We show that a Cabibbo-like coupling to light fermions is still to be expected in simple SU(5), despite the occurence of novel CP violating phases unobservable in conventional weak interactions. Proton decay cannot be 'rotated away' in this model. We compute the renormalization of the effective lagrangian due to weak and electromagnetic exchanges at short distances. (orig.)