7,679 research outputs found
Extended Skyrme Equation of State in asymmetric nuclear matter
We present a new equation of state for infinite systems (symmetric,
asymmetric and neutron matter) based on an extended Skyrme functional
constrained by microscopic Brueckner-Bethe-Goldstone results. The resulting
equation of state reproduces with very good accuracy the main features of
microscopic calculations and it is compatible with recent measurements of two
times Solar-mass neutron stars. We provide all necessary analytical expressions
to facilitate a quick numerical implementation of quantities of astrophysical
interest
Nuclear response for the Skyrme effective interaction with zero-range tensor terms. II. Sum rules and instabilities
The formalism of linear response theory for Skyrme forces including tensor
terms presented in article [1] is generalized for the case of a Skyrme energy
density functional in infinite matter. We also present analytical results for
the odd-power sum rules, with particular attention to the inverse energy
weighted sum rule, , as a tool to detect instabilities in Skyrme
functionals.Comment: Submitted to Phys. Rev.
Linear response in infinite nuclear matter as a tool to reveal finite size instabilities
Nuclear effective interactions are often modelled by simple analytical
expressions such as the Skyrme zero-range force. This effective interaction
depends on a limited number of parameters that are usually fitted using
experimental data obtained from doubly magic nuclei. It was recently shown that
many Skyrme functionals lead to the appearance of instabilities, in particular
when symmetries are broken, for example unphysical polarization of odd-even or
rotating nuclei. In this article, we show how the formalism of the linear
response in infinite nuclear matter can be used to predict and avoid the
regions of parameters that are responsible for these unphysical instabilities.Comment: Based on talk presented at 18th Nuclear Physics Workshop "Maria and
Pierre Curie", 2011, Kazimierz, Polan
Spurious finite-size instabilities in nuclear energy density functionals: spin channel
It has been recently shown, that some Skyrme functionals can lead to
non-converging results in the calculation of some properties of atomic nuclei.
A previous study has pointed out a possible link between these convergence
problems and the appearance of finite-size instabilities in symmetric nuclear
matter (SNM) around saturation density.
We show that the finite-size instabilities not only affect the ground state
properties of atomic nuclei, but they can also influence the calculations of
vibrational excited states in finite nuclei. We perform systematic fully-self
consistent Random Phase Approximation (RPA) calculations in spherical
doubly-magic nuclei. We employ several Skyrme functionals and vary the
isoscalar and isovector coupling constants of the time-odd term
. We determine critical values of these
coupling constants beyond which the RPA calculations do not converge because
RPA the stability matrix becomes non-positive.By comparing the RPA calculations
of atomic nuclei with those performed for SNM we establish a correspondence
between the critical densities in the infinite system and the critical coupling
constants for which the RPA calculations do not converge. We find a
quantitative stability criterion to detect finite-size instabilities related to
the spin term of a functional. This
criterion could be easily implemented into the standard fitting protocols to
fix the coupling constants of the Skyrme functional
Fitting Skyrme functionals using linear response theory
Recently, it has been recently shown that the linear response theory in
symmetric nuclear matter can be used as a tool to detect finite size
instabilities for different Skyrme functionals. In particular it has been shown
that there is a correlation between the density at which instabilities occur in
infinite matter and the instabilities in finite nuclei. In this article we
present a new fitting protocol that uses this correlation to add new additional
constraint in Symmetric Infinite Nuclear Matter in order to ensure the
stability of finite nuclei against matter fluctuation in all spin and isospin
channels. As an application, we give the parameters set for a new Skyrme
functional which includes central and spin-orbit parts and which is free from
instabilities by construction.Comment: Proceeding of 19th Nuclear Physics Workshop "Marie & Pierre Curie"
Kazimierz 201
Pairing correlations of cold fermionic gases at overflow from a narrow to a wide harmonic trap
Within the context of Hartree-Fock-Bogoliubov theory, we study the behavior
of superfluid Fermi systems when they pass from a small to a large container.
Such systems can be now realized thanks to recent progress in experimental
techniques. It will allow to better understand pairing properties at overflow
and in general in rapidly varying external potentials
Tools for incorporating a D-wave contribution in Skyrme energy density functionals
The possibility of adding a D-wave term to the standard Skyrme effective interaction has been widely considered in the past. Such a term has been shown to appear in the next-to-next-to-leading order of the Skyrme pseudo-potential. The aim of the present article is to provide the necessary tools to incorporate this term in a fitting procedure: first, a mean-field equation written in spherical symmetry in order to describe spherical nuclei and second, the response function to detect unphysical instabilities. With these tools it will be possible to build a new fitting procedure to determine the coupling constants of the new functional
Nuclear response for the Skyrme effective interaction with zero-range tensor terms. III. Neutron matter and neutrino propagation
The formalism of the linear response for the Skyrme energy density functional
including tensor terms derived in articles [1,2] for nuclear matter is applied
here to the case of pure neutron matter. As in article [2] we present
analytical results for the response function in all channels, the Landau
parameters and the odd-power sum rules. Special emphasis is given to the
inverse energy weighted sum rule because it can be used to detect non physical
instabilities. Typical examples are discussed and numerical results shown.
Moreover, as a direct application, neutrino propagation in neutron matter is
investigated through its neutrino mean free path at zero temperature. This
quantity turns out to be very sensitive to the tensor terms of the Skyrme
energy density functional
Skyrme effective pseudopotential up to the next-to-next-to-leading order
The explicit form of the next-to-next-to-leading order ((NLO)-L-2) of the Skyrme effective pseudopotential compatible with all required symmetries and especially with gauge invariance is presented in a Cartesian basis. It is shown in particular that for such a pseudopotential there is no spin-orbit contribution and that the D-wave term suggested in the original Skyrme formulation does not satisfy the invariance properties. The six new (NLO)-L-2 terms contribute to both the equation of state and the Landau parameters. These contributions to symmetric nuclear matter are given explicitly and discussed
Giant Monopole Resonances and nuclear incompressibilities studied for the zero-range and separable pairing interactions
Background: Following the 2007 precise measurements of monopole strengths in
tin isotopes, there has been a continuous theoretical effort to obtain a
precise description of the experimental results. Up to now, there is no
satisfactory explanation of why the tin nuclei appear to be significantly
softer than 208Pb.
Purpose: We determine the influence of finite-range and separable pairing
interactions on monopole strength functions in semi-magic nuclei.
Methods: We employ self-consistently the Quasiparticle Random Phase
Approximation on top of spherical Hartree-Fock-Bogolyubov solutions. We use the
Arnoldi method to solve the linear-response problem with pairing.
Results: We found that the difference between centroids of Giant Monopole
Resonances measured in lead and tin (about 1 MeV) always turns out to be
overestimated by about 100%. We also found that the volume incompressibility,
obtained by adjusting the liquid-drop expression to microscopic results, is
significantly larger than the infinite-matter incompressibility.
Conclusions: The zero-range and separable pairing forces cannot induce
modifications of monopole strength functions in tin to match experimental data.Comment: 11 RevTeX pages, 16 figures, 1 table, extended versio
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