SELF-CONSISTENT COUPLINGS OF PIONS AND DELTA-HOLE STATES IN NUCLEAR-MATTER

Dyson equations for the propagation of pions and DELTA's in nuclear ma tter are solved self-consistently using extended hadronic vertex funct ions to regularize the ultraviolet divergences of the loop integrals. The real part of the pion inverse propagator vanishes at only one ener gy for each momentum, unlike the conventional picture of level mixing and level repulsion for the pionic and DELTA-hole states, because of t he width of the DELTA-hole excitations. This self-consistent DELTA-hol e model is compared to data on charge-exchange reactions and used to s tudy the absorption of photons by nuclei in the DELTA-resonance region . The comparison of the baryonic vertex form factors obtained for pion ic and electromagnetic probes agrees with their interpretation as effe ctive hadronic structure functions.