F. Krmpotic et al., PROJECTED LINEAR-RESPONSE THEORY FOR CHARGE-EXCHANGE EXCITATIONS AND DOUBLE BETA-DECAY, Physics letters. Section B, 319(4), 1993, pp. 393-400
The projected random phase approximation (PRPA) for charge-exchange ex
citations is derived from the time-dependent variational principle. Ex
plicit results for the unperturbed energies (including the self-energy
corrections), the PRPA matrices, and the transition matrix elements a
re presented. The effect of the projection procedure on the two-neutri
no betabeta decay in Ge-76 is briefly discussed.