  While the no-core shell model is a state-of-the-art microscopic approach to
low-energy nuclear structure, its intense computational requirements lead us to
consider time-honored approximations such as the Hartree-Fock (HF)
approximation and the random phase approximation (RPA). We review RPA and point
out some common misunderstandings, then apply HF+RPA to the no-core shell
model. Here the main issue is appropriate treatment of contamination by
spurious center-of-mass motion.
