  Lately we have been tackling the problem of describing nuclear collective
excitations starting from correlated realistic nucleon-nucleon (NN)
interactions. The latter are constructed within the Unitary Correlation
Operator Method (UCOM), starting from realistic NN potentials. It has been
concluded that first-order RPA with a two-body UCOM interaction is not capable,
in general, of reproducing quantitatively the properties of giant resonances
(GRs), due to missing higher-order configurations and long-range correlations
as well as neglected three-body terms in the Hamiltonian.
  Here we report results on GRs obtained by employing a UCOM interaction based
on the Argonne V18 potential in Second RPA (SRPA) calculations. The same
interaction is used to describe the Hartree-Fock (HF) ground state and the
residual interactions. We find that the inclusion of second-order
configurations -- which effectively dress the underlying HF single-particle
states with self-energy insertions -- produces sizable corrections. The effect
appears essential for a realistic description of GRs when using the UCOM. We
argue that effects of higher than second order should be negligible. Therefore,
the UCOM-SRPA emerges as a promising tool for consistent calculations of
collective states in closed-shell nuclei. This is an interesting development,
given that SRPA can accommodate more physics than RPA (e.g., fragmentation).
Remaining discrepancies due to the missing three-body terms and
self-consistency issues of the present SRPA model are pointed out.
