The role of three-particle-three-hole excitations in the Gamow-Teller nuclear response

Besides exploring the Gamow-Teller response to the 2p2h excitations we also investigate the role of the 3p3h excitations in the final state, which become involved as soon as the ground-state correlations are considered. Both type of correlations in the final state are treated on the same footing. Particular emphasis is put on the conservation of the Ikeda sum rule in the framework of different approximations for the nuclear response. As an example we calculate the strength distribution in 48 Ca. We find that the combined effect of the ground state correlations and the 3p3h excitations produces a relatively small quenching of the low-lying strength compared with that generated by the 1p1h-2p2h coupling.