237 research outputs found
Faddeev treatment of long-range correlations and the one-hole spectral function of O16
The Faddeev technique is employed to study the influence of both
particle-particle and particle-hole phonons on the one-hole spectral function
of O16.
Collective excitations are accounted for at a random phase approximation
level and subsequently summed to all orders by the Faddeev equations to obtain
the nucleon self-energy. An iterative procedure is applied to investigate the
effects of the self-consistent inclusion of the fragmentation in the
determination of the phonons and the corresponding self-energy. The present
results indicate that the characteristics of hole fragmentation are related to
the low-lying states of O16.Comment: 10 pages, 6 figures, 3 tables. Submitted to Phys.Rev.
Toward a Global Dispersive Optical Model for the Driplines
A dispersive-optical-model analysis has been performed for both protons and
neutrons on 40,42,44,48Ca isotopes. The fitted potentials describe accurately
both scattering and bound quantities and extrapolate well to other stable
nuclei.
Further experimental information will be gathered to constrain extrapolations
toward the driplines.Comment: Invited talk at the "10th International Conference on Nucleus-Nucleus
Collisions", Beijing, 16-21 August 200
Role of Long-Range Correlations on the Quenching of Spectroscopic Factors
We consider the proton and neutron quasiparticle orbits around the
closed-shell 56Ni and 48Ca isotopes. It is found that large model spaces
(beyond the capability of shell-model applications) are necessary for
predicting the quenchings of spectroscopic factors.
The particle-vibration coupling is identified as the principal mechanism.
Additional correlations--due to configuration with several particle-hole
excitations--are estimated using shell-model calculations and generate an extra
reduction which is < ~4% for most quasiparticle states. The theoretical
calculations nicely agree with (e,e'p) and heavy ion knock-out experiments.
These results open a new path for a microscopic understanding of the
shell-model.Comment: Minor comments added and typos corrected. Accepted for publication on
Phys. Rev. Let
Spectroscopic Factors in 16O and Nucleon Asymmetry
The self-consistent Green's functions method is employed to study the
spectroscopic factors of quasiparticle states around 16O, 28O, 40Ca and 60Ca.
The Faddeev random phase approximation (FRPA) is used to account for the
coupling of particles with collective excitation modes. Results for 16O are
reviewed first. The same approach is applied to isotopes with large
proton-neutron asymmetry to estimate its effect on spectroscopic factors. The
results, based on the chiral N3LO force, exhibit an asymmetry dependence
similar to that observed in heavy-ion knockout experiments but weaker in
magnitude.Comment: Proceedings of the "KGU Yokohama Autumn School of Nuclear Physics",
October 9-10, 200
Faddeev description of two-hole one-particle motion and the single-particle spectral function
The Faddeev technique is employed to address the problem of describing the influence of both particle-particle and particle-hole phonons on the single-particle self-energy. The scope of the few-body Faddeev equations is extended to describe the motion of two-hole one-particle (two-particle one-hole) excitations. This formalism allows to sum both particle-particle and particle-hole phonons, obtained separately in the Random Phase Approximation. The appearance of spurious solutions for the present application of the Faddeev method is related to the inclusion of a consistent set of diagrams. The formalism presented here appears practical for finite nuclei and achieves a simultaneous inclusion of particle-particle and particle-hole phonons to all orders while the spurious solutions are properly eliminated
Quasiparticles in Neon using the Faddeev Random Phase Approximation
The spectral function of the closed-shell Neon atom is computed by expanding
the electron self-energy through a set of Faddeev equations. This method
describes the coupling of single-particle degrees of freedom with correlated
two-electron, two-hole, and electron-hole pairs. The excitation spectra are
obtained using the Random Phase Approximation, rather than the Tamm-Dancoff
framework employed in the third-order algebraic diagrammatic contruction
[ADC(3)] method. The difference between these two approaches is studied, as
well as the interplay between ladder and ring diagrams in the self-energy.
Satisfactory results are obtained for the ionization energies as well as the
energy of the ground state with the Faddeev-RPA scheme that is also appropriate
for the high-density electron gas.Comment: Revised manuscript. The working equations of the Faddeev-RPA method
are included in the Appendi
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