M. Waroquier

The spectroscopic factors for the low-lying quasihole states observed in the ¹⁶O(e,e′p)¹⁵N reaction are reinvestigated with a variational Monte Carlo calculation for the structure of the initial and final nucleus. A computational error in a previous report is rectified. It is shown that a proper treatment of center-of-mass motion does not lead to a reduction of the spectroscopic factor for p-shell quasihole states, but rather to a 7% enhancement. This is in agreement with analytical results obtained in the harmonic oscillator model. The center-of-mass effect worsens the discrepancy between present theoretical models and the experimentally observed single-particle strength. We discuss the present status of this problem, including some other mechanisms that may be relevant in this respect.

Single-particle overlap functions and spectroscopic factors are calculated using the asymptotic behavior in coordinate space of the one-body density matrix corresponding to a many-body wave function in correlated basis function theory. We include state-dependent correlation functions and discriminate between the effects of central, spin-spin, and tensor correlations. The method is applied to ¹⁶O. We also discuss the effect of center-of-mass motion on the calculated spectroscopic factors.

Long-range correlations, which are partially responsible for the observed fragmentation and depletion of low-lying single-particle strength, are studied in the Green's function formalism. The self-energy is expanded up to second order in the residual interaction. We compare two methods of implementing self-consistency in the solution of the Dyson equation beyond Hartree-Fock, for the case of the 16O nucleus. It is found that the energy-bin method and the BAGEL method lead to globally equivalent results. In both methods the final single-particle strength functions are characterized by exponential tails at energies far from the Fermi level.

It is pointed out that shell-model effects are likely to affect the energy dependence of the Δ₃₃ propagator in finite nuclei. © 1996 The American Physical Society.

A recent theorem states that for quantum many-body systems with short-range interactions the following property holds: the single-particle overlap functions, spectroscopic factors and separation energies of bound eigenstates of the (A-1)(A-1)-particle system are fully determined by the one-body density matrix of the AA-particle system in its ground state. We confirm this property, by explicit construction, for the case of a schematic, exactly solvable system.