  We present a number conserving particle-hole RPA theory for collective
excitations in the transition from normal to superfluid nuclei. The method
derives from an RPA theory developed long ago in quantum chemistry using
antisymmetric geminal powers, or equivalently number projected HFB states, as
reference states. We show within a minimal model of pairing plus monopole
interactions that the number conserving particle-hole RPA excitations evolve
smoothly across the superfluid phase transition close to the exact results,
contrary to particle-hole RPA in the normal phase and quasiparticle RPA in the
superfluid phase that require a change of basis at the broken symmetry point.
The new formalism can be applied in a straightforward manner to study
particle-hole excitations on top of a number projected HFB state.
