M. Waroquier

Nuclear overlap functions determined by the asymptotic behavior of the one-body density matrix

D. Van Neck, L. Van Daele, Y. Dewulf, M. Waroquier
Physical Review C
56 (3), 1398-1409
1997
A1
Published while none of the authors were employed at the CMM

Abstract 

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 in finite nuclei: comparison of two self-consistent treatments

Y. Dewulf, D. Van Neck, L. Van Daele, M. Waroquier
Physics Letters B
396, 7-14
1997
A1
Published while none of the authors were employed at the CMM

Abstract 

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.

Reply to ‘‘Comment on ‘Multinucleon mechanisms in (γ,N) and (γ,NN) reactions’ ’’

J. Ryckebusch, L. Machenil, M. Vanderhaeghen, V. Van der Sluys, M. Waroquier
Physical Review C
54 (6), 3313-3314
1996
A1
Published while none of the authors were employed at the CMM

Abstract 

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.

Exclusive (e,e′p) reaction at high missing momenta

V. Van der Sluys, J. Ryckebusch, M. Waroquier
Physical Review C
54 (3), 1322-1328
1996
A1
Published while none of the authors were employed at the CMM

Abstract 

The reduced (e,e′p) cross section is calculated for kinematics that probe high missing momenta. The final-state interaction is handled within a nonrelativistic many-body framework. One- and two-body nuclear currents are included. Electron distortion effects are treated in an exact distorted-wave calculation. It is shown that at high missing momenta the calculated (e,e′p) cross sections exhibit a pronounced sensitivity to ground-state correlations of the random-phase approximation type and two-body currents. The role of these mechanisms is found to be relatively small at low missing momenta. © 1996 The American Physical Society.

Single-particle properties in an exactly solvable $A$-body system

D. Van Neck, A.E.L. Dieperink, M. Waroquier
Zeitschrift für Physik
355 (2), 107-109
1996
A1
Published while none of the authors were employed at the CMM

Abstract 

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.

Natural orbitals, overlap functions, and mean-field orbitals in an exactly solvable A-body system

D. Van Neck, A.E.L. Dieperink, M. Waroquier
Physical Review C
53 (5), 2231-2242
1996
A1
Published while none of the authors were employed at the CMM

Abstract 

We consider a simple but nontrivial many-body system interacting through short-range forces, and confirm a property of such systems that was recently proposed on general grounds, namely, that single-particle overlap functions, spectroscopic factors, and separation energies of the bound (A-1)-particle eigenstates can be derived from the one-body density matrix of the A-particle system in its ground state. The basis of natural orbitals for the system is constructed and its properties are discussed. We also investigate the high-momentum content of the bound-state overlap functions and momentum distribution. It is found that the mean field provides a good approximation for the bound-state overlap functions even in the region of large momenta, where the total momentum distribution is already enhanced by several orders of magnitude over the mean-field result. © 1996 The American Physical Society.

Pion photoproduction through the Δ resonance region: relativistic versus non-relativistic unitary models

M. Vanderhaeghen, K. Heyde, J. Ryckebusch, M. Waroquier
Nuclear Physics A
595 (2), 219-258
1995
A1
Published while none of the authors were employed at the CMM

Abstract 

A fully relativistic, gauge invariant and unitary pion photoproduction model is constructed including π, ϱ, ω, N and Δ degrees of freedom. The model is compared in detail to pion photoproduction observables in view of several sets of high-quality data that were obtained through the Δ resonance region in recent years. Starting from the relativistic model, a non-relativistic model mean ffor calculations in the nuclear medium is derived. The non-relativistic model is constructed to satisfy unitarity and is applied to both charged and neutral pion photoproduction with the same parameter set.

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