IKEDA SUM-RULE, SELF-CONSISTENCY AND DOUBLE-BETA DECAY IN THE RENORMALIZED QUASI-PARTICLE RANDOM-PHASE-APPROXIMATION

The effect of the inclusion of ground-state correlations into the QRPA equation of motion for the two-neutrino double-beta (beta beta(2v)) d ecay is carefully analyzed. The resulting model, called renormalized Q RPA (RQRPA), does not collapse near the physical value of the nuclear force strength in the particle-particle channel, as happens with the o rdinary QRPA. Still, the beta beta(2v) transition amplitude is only sl ightly less sensitive on this parameter in the RQRPA than that in the plain QRPA. It is argued that this fact reveals once more that the cha racteristic behavior of the beta beta(2v) transition amplitude within the QRPA is not an artifact of the model, but a consequence of the par tial restoration of the spin-isospin SU(4) symmetry, It is shown that the price paid for bypassing the collapse in the RQRPA is the violatio n of the Ikeda sum rule.