Generalized seniority from random Hamiltonians - art. no. 014311

We investigate the generic pairing properties of shell-model many-body Hami ltonians drawn from ensembles of random two-body matrix elements. Many feat ures of pairing that are commonly attributed to the interaction are in fact seen in a large part of the ensemble space. Not only do the spectra show e vidence of pairing with favored J=0 ground states and an energy gap, but th e relationship between ground-state wave functions of neighboring nuclei sh ows signatures of pairing as well. Matrix elements of pair creation-annihil ation operators between ground states tend to be strongly enhanced. Further more, the same or similar pair operators connect several ground states alon g an isotopic chain. This algebraic structure is reminiscent of the general ized seniority model. Thus pairing may be encoded to a certain extent in th e Fock space connectivity of the interacting shell model even without speci fic features of the interaction required.