644 research outputs found
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
Non-empirical pairing energy functional in nuclear matter and finite nuclei
We study 1S0 pairing gaps in neutron and nuclear matter as well as in finite
nuclei on the basis of microscopic two-nucleon interactions. Special attention
is paid to the consistency of the pairing interaction and normal self-energy
contributions. We find that pairing gaps obtained from low-momentum
interactions depend only weakly on approximation schemes for the normal
self-energy, required in present energy-density functional calculations, while
pairing gaps from hard potentials are very sensitive to the effective-mass
approximation scheme.Comment: 14 pages, 12 figures, published versio
Tensor interaction contributions to single-particle energies
We calculate the contribution of the nucleon-nucleon tensor interaction to
single-particle energies with finite-range matrix potentials and with
zero-range Skyrme potentials. The Skx Skyrme parameters including the
zero-range tensor terms with strengths calibrated to the finite-range results
are refitted to nuclear properties. The fit allows the zero-range
proton-neutron tensor interaction as calibrated to the finite-range potential
results and that gives the observed change in the single-particle gap
(h)-(g) going from Sn to
Sn. However, the experimental dependence of the spin-orbit
splittings in Sn and Pb is not well described when the tensor
is added, due to a change in the radial dependence of the total spin-orbit
potential. The gap shift and a good fit to the -dependence can be
recovered when the like-particle tensor interaction is opposite in sign to that
required for the matrix.Comment: 5 pages, 4 figures, accepted for publication as Rapid Communication
in Physical Review
Chiral three-nucleon forces and pairing in nuclei
We present the first study of pairing in nuclei including three-nucleon
forces. We perform systematic calculations of the odd-even mass staggering
generated using a microscopic pairing interaction at first order in chiral
low-momentum interactions. Significant repulsive contributions from the leading
chiral three-nucleon forces are found. Two- and three-nucleon interactions
combined account for approximately 70% of the experimental pairing gaps, which
leaves room for self-energy and induced interaction effects that are expected
to be overall attractive in nuclei.Comment: 4 pages, 3 figure
Isovector splitting of nucleon effective masses, ab-initio benchmarks and extended stability criteria for Skyrme energy functionals
We study the effect of the splitting of neutron and proton effective masses
with isospin asymmetry on the properties of the Skyrme energy density
functional. We discuss the ability of the latter to predict observable of
infinite matter and finite nuclei, paying particular attention to controlling
the agreement with ab-initio predictions of the spin-isospin content of the
nuclear equation of state, as well as diagnosing the onset of finite size
instabilities, which we find to be of critical importance. We show that these
various constraints cannot be simultaneously fulfilled by the standard Skyrme
force, calling at least for an extension of its P-wave part.Comment: 17 pages, 9 figures; Minor changes, references added; Accepted for
publication in Phys.Rev.
Breaking and restoring symmetries within the nuclear energy density functional method
We review the notion of symmetry breaking and restoration within the frame of
nuclear energy density functional methods. We focus on key differences between
wave-function- and energy-functional-based methods. In particular, we point to
difficulties to formulate the restoration of symmetries within the energy
functional framework. The problems tackled recently in connection with
particle-number restoration serve as a baseline to the present discussion.
Reaching out to angular-momentum restoration, we identify an exact mathematical
property of the energy density that could be used to
constrain energy density functional kernels. Consequently, we suggest possible
routes towards a better formulation of symmetry restorations within energy
density functional methods.Comment: 16 pages, 3 figures, contribution to the "Focus issue on Open
Problems in Nuclear Structure", Journal of Physics
Towards heavy-mass ab initio nuclear structure: Open-shell Ca, Ni and Sn isotopes from Bogoliubov coupled-cluster theory
Recent developments in nuclear many-body theory enabled the description of
open-shell medium-mass nuclei from first principles by exploiting the
spontaneous breaking of symmetries within correlation expansion methods. Once
combined with systematically improvable inter-nucleon interactions consistently
derived from chiral effective field theory, modern ab initio nuclear structure
calculations provide a powerful framework to deliver first-principle
predictions accompanied with theoretical uncertainties. In this Letter,
controlled ab initio Bogoliubov coupled cluster calculations are performed for
the first time, targeting the ground-state of all calcium, nickel and tin
isotopes up to mass . While showing good agreement with available
experimental data, the shell structure evolution in neutron-rich isotopes and
the location of the neutron drip-lines are predicted.Comment: 7 pages, 5 figure
Summary report of the Standards, Options and Recommendations for malnutrition and nutritional assessment in patients with cancer (1999)
Instabilities in the Nuclear Energy Density Functional
In the field of Energy Density Functionals (EDF) used in nuclear structure
and dynamics, one of the unsolved issues is the stability of the functional.
Numerical issues aside, some EDFs are unstable with respect to particular
perturbations of the nuclear ground-state density. The aim of this contribution
is to raise questions about the origin and nature of these instabilities, the
techniques used to diagnose and prevent them, and the domain of density
functions in which one should expect a nuclear EDF to be stable.Comment: Special issue "Open Problems in Nuclear Structure Theory" of
Jour.Phys.G - accepted. 7 pages, 2 figure
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