67 research outputs found
Do halos exist on the dripline of deformed nuclei?
A study of the effect of deformation and pairing on the development of halo
nuclei is presented. Exploratory three-body calculations show that
both the NN interaction and the deformation/excitation of the core hinder the
formation of the halo. Preliminary self-consistent mean-field calculations are
used to search for regions in the nuclear chart where halos could potentially
develop. These are also briefly discussed.Comment: 5 pages and 3 figures, proceedings for CGS1
TIME-DEPENDENT HARTREE-FOCK DESCRIPTION OF HEAVY IONS FUSION
A microscopic mean-field description of heavy ions fusion is performed in the framework of the Time-Dependent Hartree-Fock (TDHF) theory using a Skyrme interaction with the SLy4d parametrization. A good agreement with experiments is obtained on the position of the fusion barriers for various total masses, mass asymmetries and deformations. The excitation function of the 16O+208Pb is overestimated by about 16% above the barrier. The restriction to an independent particles state in the mean-field dynamics prevents the description of sub-barrier fusion. Effect of transfer on fusion is discussed
Structure and direct decay of Giant Monopole Resonances
We study structure and direct decay of the Giant Monopole Resonance (GMR) at
the RPA level using the Time-Dependent Energy Density Functional method in the
linear response regime in a few doubly-magic nuclei. A proper treatment of the
continuum, through the use of large coordinate space, allows for a separation
between the nucleus and its emitted nucleons. The microscopic structure of the
GMR is investigated with the decomposition of the strength function into
individual single-particles quantum numbers. A similar microscopic
decomposition of the spectra of emitted nucleons by direct decay of the GMR is
performed. In this harmonic picture of giant resonance, shifting every
contribution by the initial single-particle energy allows to reconstruct the
GMR strength function. The RPA residual interaction couples bound 1-particle
1-hole states to unbound ones, allowing for the total decay of the GMR. In this
article, we then intend to get an understanding of the direct decay mechanism
from coherent one-particle-one-hole superpositions, while neglecting more
complex configurations. Time-dependent beyond mean-field approaches should be
use, in the future, to extend this method.Comment: 11 pages, 10 figures. Major revisions including new formal
development, new calculations and figures, comparison to experimental data
and added references and discussion
Pairing Vibrations Study with the Time-Dependent Hartree-Fock-Bogoliubov theory
International audienceWe study pairing vibrations in O and Ca nuclei solving the time-dependent Hartree-Fock-Bogoliubov equation in coordinate space with spherical symmetry. We use the SLy4 Skyrme functional in the normal part of the energy density functional and a local density dependent functional in its pairing part. Pairing vibrations are excited by two-neutron transfer operators. Strength distributions are obtained using the Fourier transform of the time-dependent response of two-neutron pair-transfer observables in the linear regime. Results are in overall agreement with quasiparticle random phase approximation calculations for Oxygen isotopes, though differences appear when increasing the neutron number. Both low lying pairing modes and giant pairing vibrations (GPV) are discussed. The GPV is observed in the Oxygen but not in the Calcium isotopes
Symmetry restoration for odd-mass nuclei with a Skyrme energy density functional
In these proceedings, we report first results for particle-number and
angular-momentum projection of self-consistently blocked triaxial
one-quasiparticle HFB states for the description of odd-A nuclei in the context
of regularized multi-reference energy density functionals, using the entire
model space of occupied single-particle states. The SIII parameterization of
the Skyrme energy functional and a volume-type pairing interaction are used.Comment: 8 pages, 3 figures, workshop proceeding
Beyond Mean-Field Calculations for Odd-A Nuclei
Beyond mean-field methods are very successful tools for the description of
large-amplitude collective motion for even-even atomic nuclei. The
state-of-the-art framework of these methods consists in a Generator Coordinate
Method based on angular-momentum and particle-number projected triaxially
deformed Hatree-Fock-Bogoliubov (HFB) states. The extension of this scheme to
odd-mass nuclei is a long-standing challenge. We present for the first time
such an extension, where the Generator Coordinate space is built from
self-consistently blocked one-quasiparticle HFB states. One of the key points
for this success is that the same Skyrme interaction is used for the mean-field
and the pairing channels, thus avoiding problems related to the violation of
the Pauli principle. An application to 25Mg illustrates the power of our
method, as agreement with experiment is obtained for the spectrum,
electromagnetic moments, and transition strengths, for both positive and
negative parity states and without the necessity for effective charges or
effective moments. Although the effective interaction still requires
improvement, our study opens the way to systematically describe odd-A nuclei
throughout the nuclear chart.Comment: 5 pages, 3 figure
Evaluation of overlaps between arbitrary Fermionic quasiparticle vacua
We derive an expression that allows for the unambiguous evaluation of the
overlap between two arbitrary quasiparticle vacua, including its sign. Our
expression is based on the Pfaffian of a skew-symmetric matrix, extending the
formula recently proposed by [L. M. Robledo, Phys. Rev. C 79, 021302(R) (2009)]
to the most general case, including the one of the overlap between two
different blocked n-quasiparticle states for either even or odd systems. The
powerfulness of the method is illustrated for a few typical matrix elements
that appear in realistic angular-momentum-restored Generator-Coordinate Method
calculations when breaking time-reversal invariance and using the full model
space of occupied single-particle states.Comment: 10 pages, 3 figure
The Random Discrete Action for 2-Dimensional Spacetime
A one-parameter family of random variables, called the Discrete Action, is
defined for a 2-dimensional Lorentzian spacetime of finite volume. The single
parameter is a discreteness scale. The expectation value of this Discrete
Action is calculated for various regions of 2D Minkowski spacetime. When a
causally convex region of 2D Minkowski spacetime is divided into subregions
using null lines the mean of the Discrete Action is equal to the alternating
sum of the numbers of vertices, edges and faces of the null tiling, up to
corrections that tend to zero as the discreteness scale is taken to zero. This
result is used to predict that the mean of the Discrete Action of the flat
Lorentzian cylinder is zero up to corrections, which is verified. The
``topological'' character of the Discrete Action breaks down for causally
convex regions of the flat trousers spacetime that contain the singularity and
for non-causally convex rectangles.Comment: 20 pages, 10 figures, Typos correcte
On the causal properties of warped product spacetimes
It is shown that the warped product spacetime P=M *_f H, where H is a
complete Riemannian manifold, and the original spacetime M share necessarily
the same causality properties, the only exceptions being the properties of
causal continuity and causal simplicity which present some subtleties. For
instance, it is shown that if diamH=+\infty, the direct product spacetime P=M*H
is causally simple if and only if (M,g) is causally simple, the Lorentzian
distance on M is continuous and any two causally related events at finite
distance are connected by a maximizing geodesic. Similar conditions are found
for the causal continuity property. Some new results concerning the behavior of
the Lorentzian distance on distinguishing, causally continuous, and causally
simple spacetimes are obtained. Finally, a formula which gives the Lorentzian
distance on the direct product in terms of the distances on the two factors
(M,g) and (H,h) is obtained.Comment: 22 pages, 2 figures, uses the package psfra
Linear Responses in Time-dependent Hartree-Fock-Bogoliubov Method with Gogny Interaction
A numerical method to integrate the time-dependent Hartree-Fock Bogoliubov
(TDHFB) equations with Gogny interaction is proposed. The feasibility of the
TDHFB code is illustrated by the conservation of the energy, particle numbers,
and center-of-mass in the small amplitude vibrations of oxygen 20. The TDHFB
code is applied to the isoscalar quadrupole and/or isovector dipole vibrations
in the linear (small amplitude) region in oxygen isotopes (masses A = 18,20,22
and 24), titanium isotopes (A = 44,50,52 and 54), neon isotope (A = 26), and
magnesium isotopes (A = 24 and 34). The isoscalar quadrupole and isovector
dipole strength functions are calculated from the expectation values of the
isoscalar quadrupole and isovector dipole moments.Comment: 10 pages, 13 figure
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