Description of the 2νββ decay within a fully renormalised RPA approach

The RPA treatment of a many body Hamiltonian describing the states of even-even nuclei involved in a 2νββ decay is revisited. One shows that renormalizing the dipole two quasiparticle operators by accounting for new correlations in the ground state requires a similar renormalization for the dipole density operators which results in activating new boson degrees of freedom. Possible consequences on the Ikeda sum rule and Gamow-Teller transition amplitude are suggested. A numerical application for a two level model is presented (orig.)