  In the framework of the ab-initio no-core shell model (NCSM), we describe the
longitudinal-longitudinal distribution function, part of the inclusive (e,e')
longitudinal response. In the two-body cluster approximation, we compute the
effective operators consistent with the unitary transformation used to obtain
the effective Hamiltonian. When short-range correlations are probed, the
results display independence from the model space size and length scale.
Long-range correlations are more difficult to model in the NCSM and they can be
described only by increasing the model space or increasing the cluster size. In
order to illustrate the model space independence for short-range observables,
we present results for a large set of model spaces for 4He, and in 0-4hw model
spaces for 12C.
