1,269 research outputs found
Nuclear single-particle states: dynamical shell model and energy density functional methods
We discuss different approaches to the problem of reproducing the observed
features of nuclear single-particle (s.p.) spectra. In particular, we analyze
the dominant energy peaks, and the single-particle strength fragmentation,
using the example of neutron states in 208Pb. Our main emphasis is the
interpretation of that fragmentation as due to particle-vibration coupling
(PVC). We compare with recent Energy Density Functional (EDF) approaches, and
try to present a critical perspective.Comment: 7 pages. Contribution to the "Focus issue on Open Problems in Nuclear
Structure", Journal of Physics
Quasi-particle random phase approximation with quasi-particle-vibration coupling: application to the Gamow-Teller response of the superfluid nucleus Sn
We propose a self-consistent quasi-particle random phase approximation (QRPA)
plus quasi-particle-vibration coupling (QPVC) model with Skyrme interactions to
describe the width and the line shape of giant resonances in open-shell nuclei,
in which the effect of superfluidity should be taken into account in both the
ground state and the excited states. We apply the new model to the Gamow-Teller
resonance in the superfluid nucleus Sn, including both the isoscalar
spin-triplet and the isovector spin-singlet pairing interactions. The strength
distribution in Sn is well reproduced and the underlying microscopic
mechanisms, related to QPVC and also to isoscalar pairing, are analyzed in
detail.Comment: 32 pages, 11 figures, 4 table
Effects of the Tensor Force on the Multipole Response in Finite Nuclei
We present a thorough analysis of the effects of the tensor interaction on
the multipole response of magic nuclei, using the fully self-consistent Random
Phase Approximation (RPA) model with Skyrme interactions. We disentangle the
modifications to the static mean field induced by the tensor terms, and the
specific features of the residual particle-hole (p-h) tensor interaction, for
quadrupole (2+), octupole (3-), and also magnetic dipole (1+) responses. It is
pointed out that the tensor force has a larger effect on the magnetic dipole
states than on the natural parity states 2+ and 3-, especially at the mean
field level. Perspectives for a better assessment of the tensor force
parameters are eventually discussed
Heat conduction induced by non-Gaussian athermal fluctuations
We study the properties of heat conduction induced by non-Gaussian noises
from athermal environments. We find that new terms should be added to the
conventional Fourier law and the fluctuation theorem for the heat current,
where its average and fluctuation are determined not only by the noise
intensities but also by the non-Gaussian nature of the noises. Our results
explicitly show the absence of the zeroth law of thermodynamics in athermal
systems.Comment: 15 pages, 4 figures, PRE in pres
Entanglement versus mutual information in quantum spin chains
The quantum entanglement of a bipartite quantum Ising chain is compared
with the mutual information between the two parts after a local measurement
of the classical spin configuration. As the model is conformally invariant, the
entanglement measured in its ground state at the critical point is known to
obey a certain scaling form. Surprisingly, the mutual information of classical
spin configurations is found to obey the same scaling form, although with a
different prefactor. Moreover, we find that mutual information and the
entanglement obey the inequality in the ground state as well as in a
dynamically evolving situation. This inequality holds for general bipartite
systems in a pure state and can be proven using similar techniques as for
Holevo's bound.Comment: 10 pages, 3 figure
The Spectral Line Shape of Exotic Nuclei
The quadrupole strength function of is calculated making use of the
SIII interaction, within the framework of continuum-RPA and taking into account
collisions among the nucleons (doorway coupling). The centroid of the giant
resonance is predicted at MeV, that is much below the energy
expected for both isoscalar and isovector quadrupole resonances in nuclei along
the stability valley. About half of this width arises from the coupling of the
resonance to the continuum and about half is due to doorway coupling. This
result is similar to that obtained in the study of giant resonances in light,
-stable nuclei, and shows the lack of basis for the expectation,
entertained until now in the literature, that continuum decay was the main
damping mechanism of giant resonances in halo nuclei.Comment: LaTeX file, 7 pages, figures not included but available if requested
at [email protected], accepted for publication in Phys. Rev.
Widths of Isobaric Analog Resonances: a microscopic approach
A self-consistent particle-phonon coupling model is used to investigate the
properties of the isobaric analog resonance in Bi. It is shown that
quantitative agreement with experimental data for the energy and the width can
be obtained if the effects of isospin-breaking nuclear forces are included, in
addition to the Coulomb force effects. A connection between microscopic model
predictions and doorway state approaches which make use of the isovector
monopole resonance, is established via a phenomenological ansatz for the
optical potential.Comment: 18 pages, 1 figure. To appear on Phys. Rev. C (tentatively scheduled
for June 1998
Effect of the tensor force on the charge-exchange spin-dipole excitations of 208Pb
The charge-exchange spin-dipole (SD) excitations of 208Pb are studied by
using a fully self-consistent Skyrme Hartree-Fock plus Random Phase
Approximation (HF+RPA) formalism which includes the tensor interaction. It is
found, for the first time, that the tensor correlations have a unique,
multipole-dependent effect on the SD excitations, that is, they produce
softening of 1- states, but hardening of 0- and 2- states. This paves the way
to a clear assessment of the strength of the tensor terms. We compare our
results with a recent measurement, showing that our choice of tensor terms
improves the agreement with experiment. The robustness of our results is
supported by the analytic form of the tensor matrix elements.Comment: 4 pages, 1 figure, 2 table
Extended sudden approximation model for high-energy nucleon removal reactions
A model based on the sudden approximation has been developed to describe high
energy single nucleon removal reactions. Within this approach, which takes as
its starting point the formalism of Hansen \cite{Anne2}, the nucleon-removal
cross section and the full 3-dimensional momentum distributions of the core
fragments including absorption, diffraction, Coulomb and nuclear-Coulomb
interference amplitudes, have been calculated. The Coulomb breakup has been
treated to all orders for the dipole interaction. The model has been compared
to experimental data for a range of light, neutron-rich psd-shell nuclei. Good
agreement was found for both the inclusive cross sections and momentum
distributions. In the case of C, comparison is also made with the
results of calculations using the transfer-to-the-continuum model. The
calculated 3-dimensional momentum distributions exhibit longitudinal and
transverse momentum components that are strongly coupled by the reaction for
s-wave states, whilst no such effect is apparent for d-waves. Incomplete
detection of transverse momenta arising fromlimited experimental acceptances
thus leads to a narrowing of the longitudinal distributions for nuclei with
significant s-wave valence neutron configurations, as confirmed by the data.
Asymmetries in the longitudinal momentum distributions attributed to
diffractive dissociation are also explored.Comment: 16 figures, submitted to Phys. Rev.
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