  We discuss the implications of using an intrinsic Hamiltonian in theories
without particle-number conservation, e.g., the Hartree-Fock-Bogoliubov
approximation, where the Hamiltonian's particle-number dependence leads to
discrepancies if one naively replaces the particle-number operator by its
expectation value. We develop a systematic expansion that fixes this problem
and leads to an a posteriori justification of the widely-used one- plus
two-body form of the intrinsic kinetic energy in nuclear self-consistent field
methods. The expansion's convergence properties as well as its practical
applications are discussed for several sample nuclei.
