4,721 research outputs found
Natural Units For Nuclear Energy Density Functional Theory
Naive dimensional analysis based on chiral effective theory, when adapted to
nuclear energy density functionals, prescribes natural units and a hierarchy of
contributions that could be used to constrain fits of generalized functionals.
By applying these units, a large sample of Skyrme parametrizations is examined
for naturalness, which is signaled by dimensionless coupling constants of order
one. The bulk of the parameters are found to be natural, with an underlying
scale consistent with other determinations. Significant deviations from unity
are associated with deficiencies in the corresponding terms of particular
functionals or with an incomplete optimization procedure.Comment: 5 pages, 2 figures, accepted for publication in Phys. Rev.
Neutron skin uncertainties of Skyrme energy density functionals
Background: Neutron-skin thickness is an excellent indicator of isovector
properties of atomic nuclei. As such, it correlates strongly with observables
in finite nuclei that depend on neutron-to-proton imbalance and the nuclear
symmetry energy that characterizes the equation of state of neutron-rich
matter. A rich worldwide experimental program involving studies with rare
isotopes, parity violating electron scattering, and astronomical observations
is devoted to pinning down the isovector sector of nuclear models. Purpose: We
assess the theoretical systematic and statistical uncertainties of neutron-skin
thickness and relate them to the equation of state of nuclear matter, and in
particular to nuclear symmetry energy parameters. Methods: We use the nuclear
superfluid Density Functional Theory with several Skyrme energy density
functionals and density dependent pairing. To evaluate statistical errors and
their budget, we employ the statistical covariance technique. Results: We find
that the errors on neutron skin increase with neutron excess. Statistical
errors due to uncertain coupling constants of the density functional are found
to be larger than systematic errors, the latter not exceeding 0.06 fm in most
neutron-rich nuclei across the nuclear landscape. The single major source of
uncertainty is the poorly determined slope L of the symmetry energy that
parametrizes its density dependence. Conclusions: To provide essential
constraints on the symmetry energy of the nuclear energy density functional,
next-generation measurements of neutron skins are required to deliver precision
better than 0.06 fm.Comment: 5 pages, 4 figure
Nuclear DFT electromagnetic moments of intruder configurations calculated in heavy deformed open-shell odd nuclei with 63<=Z<=82 and 82<=N<=126
Within the nuclear DFT approach, we determined the magnetic dipole and
electric quadrupole moments for paired nuclear states corresponding to the
proton (neutron) quasiparticles blocked in the p11/2- (n13/2+) intruder
configurations. We performed calculations for all deformed open-shell odd
nuclei with 63<=Z<=82 and 82<=N<=126. Time-reversal symmetry was broken in the
intrinsic reference frame and self-consistent shape and spin core polarizations
were established. We determined spectroscopic moments of
angular-momentum-projected wave functions and compared them with available
experimental data. We obtained good agreement with data without using effective
g-factors or effective charges in the dipole or quadrupole operators,
respectively. We also showed that the intrinsic magnetic dipole moments, or
those obtained for conserved intrinsic time-reversal symmetry, do not represent
viable approximations of the spectroscopic ones.Comment: 11 RevTex pages, 9 figure
Computing Heavy Elements
Reliable calculations of the structure of heavy elements are crucial to
address fundamental science questions such as the origin of the elements in the
universe. Applications relevant for energy production, medicine, or national
security also rely on theoretical predictions of basic properties of atomic
nuclei. Heavy elements are best described within the nuclear density functional
theory (DFT) and its various extensions. While relatively mature, DFT has never
been implemented in its full power, as it relies on a very large number (~
10^9-10^12) of expensive calculations (~ day). The advent of leadership-class
computers, as well as dedicated large-scale collaborative efforts such as the
SciDAC 2 UNEDF project, have dramatically changed the field. This article gives
an overview of the various computational challenges related to the nuclear DFT,
as well as some of the recent achievements.Comment: Proceeding of the Invited Talk given at the SciDAC 2011 conference,
Jul. 10-15, 2011, Denver, C
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