1,154 research outputs found
Microscopic calculations and energy expansions for neutron-rich matter
We investigate asymmetric nuclear matter with two- and three-nucleon
interactions based on chiral effective field theory, where three-body forces
are fit only to light nuclei. Focusing on neutron-rich matter, we calculate the
energy for different proton fractions and include estimates of the theoretical
uncertainty. We use our ab-initio results to test the quadratic expansion
around symmetric matter with the symmetry energy term, and confirm its validity
for highly asymmetric systems. Our calculations are in remarkable agreement
with an empirical parametrization for the energy density. These findings are
very useful for astrophysical applications and for developing new equations of
state.Comment: 15 pages, 9 figures, published versio
Ab-initio self-consistent Gorkov-Green's function calculations of semi-magic nuclei - II. Numerical implementation at second order with a two-nucleon interaction
The newly developed Gorkov-Green's function approach represents a promising
path to the ab initio description of medium-mass open-shell nuclei. We discuss
the implementation of the method at second order with a two-body interaction,
with particular attention to the numerical solution of Gorkov's equation.
Different sources of theoretical error and degrees of self-consistency are
investigated. We show that Krylov projection techniques with a multi-pivot
Lanczos algorithm efficiently handle the growth of poles in the one-body
Green's function when Gorkov's equation is solved self-consistently. The end
result is a tractable, accurate and gently scaling ab initio scheme applicable
to full isotopic chains in the medium-mass region.Comment: 17 pages, 13 figure
Ab-initio Gorkov-Green's function calculations of open-shell nuclei
We present results from a new ab-initio method that uses the self-consistent
Gorkov Green's function theory to address truly open-shell systems. The
formalism has been recently worked out up to second order and is implemented
here in nuclei for the first time on the basis of realistic nuclear forces. We
find good convergence of the results with respect to the basis size in Ca44 and
Ni74 and discuss quantities of experimental interest including ground-state
energies, pairing gaps and particle addition/removal spectroscopy. These
results demonstrate that the Gorkov method is a valid alternative to
multireference approaches for tackling degenerate or near degenerate quantum
systems. In particular, it increases the number of mid-mass nuclei accessible
in an ab-initio fashion from a few tens to a few hundreds.Comment: 5 pages, 3 figure
Toward the Ab-initio Description of Medium Mass Nuclei
As ab-initio calculations of atomic nuclei enter the A=40-100 mass range, a
great challenge is how to approach the vast majority of open-shell (degenerate)
isotopes. We add realistic three-nucleon interactions to the state of the art
many-body Green's function theory of closed-shells, and find that physics of
neutron driplines is reproduced with very good quality. Further, we introduce
the Gorkov formalism to extend ab-initio theory to semi-magic, fully
open-shell, isotopes. Proof-of-principle calculations for Ca-44 and Ni-74
confirm that this approach is indeed feasible. Combining these two advances
(open-shells and three-nucleon interactions) requires longer, technical, work
but it is otherwise within reach.Comment: Contribution to Summary Report of EURISOL Topical and Town Meetings,
15-19 October 2012; missing affiliations added and corrected errors in Tab
Self-consistent Gorkov Green's function calculations of one-nucleon spectral properties
Results from the newly developed Gorkov self-consistent Green's function approach are presented. Ab-initio spectral strength distributions for one-nucleon addition or removal calculated in doubly-closed shell 40Ca and in semi-magic 44Ca are briefly discussed. The object of the present communication is to illustrate the potential spectroscopic reach of the method
Gorkov self-consistent Green's function calculations of semi-magic nuclei
The first nuclear structure application of the newly developed Gorkov self-consistent Green's function method is presented. The approach aims to describe many-nucleon systems from an ab-initio standpoint featuring an explicit treatment of pairing correlations. In the present work calculations of binding energies of calcium isotopes are reported and compared with experimental data and other theoretical references
In medium T-matrix for nuclear matter with three-body forces - binding energy and single particle properties
We present spectral calculations of nuclear matter properties including
three-body forces. Within the in-medium T-matrix approach, implemented with the
CD-Bonn and Nijmegen potentials plus the three-nucleon Urbana interaction, we
compute the energy per particle in symmetric and neutron matter. The three-body
forces are included via an effective density dependent two-body force in the
in-medium T-matrix equations. After fine tuning the parameters of the
three-body force to reproduce the phenomenological saturation point in
symmetric nuclear matter, we calculate the incompressibility and the energy per
particle in neutron matter. We find a soft equation of state in symmetric
nuclear matter but a relatively large value of the symmetry energy. We study
the the influence of the three-body forces on the single-particle properties.
For symmetric matter the spectral function is broadened at all momenta and all
densities, while an opposite effect is found for the case of neutrons only.
Noticeable modification of the spectral functions are realized only for
densities above the saturation density. The modifications of the self-energy
and the effective mass are not very large and appear to be strongly suppressed
above the Fermi momentum.Comment: 20 pages, 11 figure
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