782 research outputs found
Symmetry conserving non-perturbative s-wave renormalization of the pion in hot and baryon dense medium
A non-perturbative s-wave renormalization of the pion in a hot and baryon
rich medium is presented. This approach proceeds via a mapping of the canonical
pion into the axial Noether's charge. The mapping was made dynamical in the
Hartree-Fock-Bogoliubov random phase approximation (HFB-RPA). It is shown that
this approach, while order mixing, is still symmetry conserving both in the
baryon free and baryon rich sectors, at zero as well as finite temperature. The
systematic character of this approach is emphasized and it is particularly
argued that it may constitute an interesting alternative for the
non-perturbative assessment of the nuclear matter saturation properties.Comment: Latex, 22 pages, 3 figure
The tensor part of the Skyrme energy density functional. III. Time-odd terms at high spin
This article extends previous studies on the effect of tensor terms in the
Skyrme energy density functional by breaking of time-reversal invariance. We
have systematically probed the impact of tensor terms on properties of
superdeformed rotational bands calculated within the cranked
Hartree-Fock-Bogoliubov approach for different parameterizations covering a
wide range of values for the isoscalar and isovector tensor coupling constants.
We analyze in detail the contribution of the tensor terms to the energies and
dynamical moments of inertia and study their impact on quasi-particle spectra.
Special attention is devoted to the time-odd tensor terms, the effect of
variations of their coupling constants and finite-size instabilities.Comment: 28 pages, 34 figure
Time-odd mean fields in covariant density functional theory: Rotating systems
Time-odd mean fields (nuclear magnetism) and their impact on physical
observables in rotating nuclei are studied in the framework of covariant
density functional theory (CDFT). It is shown that they have profound effect on
the dynamic and kinematic moments of inertia. Particle number, configuration
and rotational frequency dependences of their impact on the moments of inertia
have been analysed in a systematic way. Nuclear magnetism can also considerably
modify the band crossing features such as crossing frequencies and the
properties of the kinematic and dynamic moments of inertia in the band crossing
region. The impact of time-odd mean fields on the moments of inertia in the
regions away from band crossing only weakly depends on the relativistic mean
field parametrization, reflecting good localization of the properties of
time-odd mean fields in CDFT. The moments of inertia of normal-deformed nuclei
considerably deviate from the rigid body value. On the contrary, superdeformed
and hyperdeformed nuclei have the moments of inertia which are close to rigid
body value. The structure of the currents in rotating frame, their microscopic
origin and the relations to the moments of inertia have been systematically
analysed. The phenomenon of signature separation in odd-odd nuclei, induced by
time-odd mean fields, has been analysed in detail.Comment: 20 pages. 16 figure
Isovector Giant Dipole Resonance of Stable Nuclei in a Consistent Relativistic Random Phase Approximation
A fully consistent relativistic random phase approximation is applied to
study the systematic behavior of the isovector giant dipole resonance of nuclei
along the -stability line in order to test the effective Lagrangians
recently developed. The centroid energies of response functions of the
isovector giant dipole resonance for stable nuclei are compared with the
corresponding experimental data and the good agreement is obtained. It is found
that the effective Lagrangian with an appropriate nuclear symmetry energy,
which can well describe the ground state properties of nuclei, could also
reproduce the isovector giant dipole resonance of nuclei along the
-stability line.Comment: 4 pages, 1 Postscript figure, to be submitted to Chin.Phys.Let
Configuration Mixing within the Energy Density Functional Formalism: Removing Spurious Contributions from Non-Diagonal Energy Kernels
Multi-reference calculations along the lines of the Generator Coordinate
Method or the restoration of broken symmetries within the nuclear Energy
Density Functional (EDF) framework are becoming a standard tool in nuclear
structure physics. These calculations rely on the extension of a
single-reference energy functional, of the Gogny or the Skyrme types, to
non-diagonal energy kernels. There is no rigorous constructive framework for
this extension so far. The commonly accepted way proceeds by formal analogy
with the expressions obtained when applying the generalized Wick theorem to the
non-diagonal matrix element of a Hamilton operator between two product states.
It is pointed out that this procedure is ill-defined when extended to EDF
calculations as the generalized Wick theorem is taken outside of its range of
applicability. In particular, such a procedure is responsible for the
appearance of spurious divergences and steps in multi-reference EDF energies,
as was recently observed in calculations restoring particle number or angular
momentum. In the present work, we give a formal analysis of the origin of this
problem for calculations with and without pairing, i.e. constructing the
density matrices from either Slater determinants or quasi-particle vacua. We
propose a correction to energy kernels that removes the divergences and steps,
and which is applicable to calculations based on any symmetry restoration or
generator coordinate. The method is formally illustrated for particle number
restoration and is specified to configuration mixing calculations based on
Slater determinants.Comment: 27 pages, 1 figure, accepted for publication in PR
Density functional theory and Kohn-Sham scheme for self-bound systems
We demonstrate how the separation of the total energy of a self-bound system
into a functional of the internal one-body Fermionic density and a function of
an arbitrary wave vector describing the center-of-mass kinetic energy can be
used to set-up an "internal" Kohn-Sham scheme.Comment: 6 pages. To be published in Phys. Rev.
Time-odd mean fields in covariant density functional theory I. Non-rotating systems
Time-odd mean fields (nuclear magnetism) are analyzed in the framework of
covariant density functional theory (CDFT). It is shown that they always
provide additional binding to the binding energies of odd-mass nuclei. This
additional binding only weakly depends on the RMF parametrization reflecting
good localization of the properties of time-odd mean fields in CDFT. The
underlying microscopic mechanism is discussed in detail. Time-odd mean fields
affect odd-even mass differences. However, our analysis suggests that the
modifications of the strength of pairing correlations required to compensate
for their effects are modest. In contrast, time-odd mean fields have profound
effect on the properties of odd-proton nuclei in the vicinity of proton-drip
line. Their presence can modify the half-lives of proton-emitters (by many
orders of magnitude in light nuclei) and affect considerably the possibilities
of their experimental observation.Comment: 20 pages, 19 figure
The Liquid-Gas Phase Transitions in a Multicomponent Nuclear System with Coulomb and Surface Effects
The liquid-gas phase transition is studied in a multi-component nuclear
system using a local Skyrme interaction with Coulomb and surface effects. Some
features are qualitatively the same as the results of Muller and Serot which
uses relativistic mean field without Coulomb and surface effects. Surface
tension brings the coexistance binodal surface to lower pressure. The Coulomb
interaction makes the binodal surface smaller and cause another pair of binodal
points at low pressure and large proton fraction with less protons in liquid
phase and more protons in gas phase.Comment: 20 pages including 7 postscript figure
Shell Structure and Strengthening of Superconducting Pair Correlation in Nanoclusters
The existence of shell structure and the accompanying high degeneracy of
electronic levels leads to the possibility of strong superconducting pairing in
metallic nanoclusters with N~100-1000 delocalized electrons. The most favorable
cases correspond to (a) "magic" clusters with strongly degenerate highest
occupied and lowest unoccupied shells and a relatively small energy spacing
between them as well as to (b) clusters with slightly incomplete shells and
small Jahn-Teller splitting. It is shown that realistic sets of parameters lead
to very high values of Tc as well as to a strong alteration of the energy
spectrum. The impact of fluctuations is analyzed. Spectroscopic experiments
aimed at detecting the presence of pair correlations are proposed. The pairing
should also manifest itself via odd-even effects in cluster spectra, similar to
the case of nuclei
Pairing Properties In Relativistic Mean Field Models Obtained From Effective Field Theory
We apply recently developed effective field theory nuclear models in mean
field approximation (parameter sets G1 and G2) to describe ground-state
properties of nuclei from the valley of -stability up to the drip lines.
For faster calculations of open-shell nuclei we employ a modified BCS approach
which takes into account quasi-bound levels owing to their centrifugal barrier,
with a constant pairing strength. We test this simple prescription by comparing
with available Hartree-plus-Bogoliubov results. Using the new effective
parameter sets we then compute separation energies, density distributions and
spin--orbit potentials in isotopic (isotonic) chains of nuclei with magic
neutron (proton) numbers. The new forces describe the experimental systematics
similarly to conventional non-linear relativistic force
parameters like NL3.Comment: 29 pages, 17 figures, accepted for publication in PR
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