63 research outputs found
-decay half-lives of neutron-rich nuclei and matter flow in the -process
The -decay half-lives of neutron-rich nuclei with are systematically investigated using the newly developed fully
self-consistent proton-neutron quasiparticle random phase approximation (QRPA),
based on the spherical relativistic Hartree-Fock-Bogoliubov (RHFB) framework.
Available data are reproduced by including an isospin-dependent proton-neutron
pairing interaction in the isoscalar channel of the RHFB+QRPA model. With the
calculated -decay half-lives of neutron-rich nuclei a remarkable
speeding up of -matter flow is predicted. This leads to enhanced -process
abundances of elements with , an important result for the
understanding of the origin of heavy elements in the universe.Comment: 14 pages, 4 figure
Superallowed Fermi transitions in RPA with a relativistic point-coupling energy functional
The self-consistent random phase approximation (RPA) approach with the
residual interaction derived from a relativistic point-coupling energy
functional is applied to evaluate the isospin symmetry-breaking corrections
{\delta}c for the 0+\to0+ superallowed Fermi transitions. With these {\delta}c
values, together with the available experimental ft values and the improved
radiative corrections, the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM)
matrix is examined. Even with the consideration of uncertainty, the sum of
squared top-row elements has been shown to deviate from the unitarity condition
by 0.1% for all the employed relativistic energy functionals.Comment: 13 pages,2 figure
Beyond the relativistic mean-field approximation: configuration mixing of angular momentum projected wave functions
We report the first study of restoration of rotational symmetry and
fluctuations of the quadrupole deformation in the framework of relativistic
mean-field models. A model is developed which uses the generator coordinate
method to perform configuration mixing calculations of angular momentum
projected wave functions, calculated in a relativistic point-coupling model.
The geometry is restricted to axially symmetric shapes, and the intrinsic wave
functions are generated from the solutions of the constrained relativistic
mean-field + BCS equations in an axially deformed oscillator basis. A number of
illustrative calculations are performed for the nuclei 194Hg and 32Mg, in
comparison with results obtained in non-relativistic models based on Skyrme and
Gogny effective interactions.Comment: 32 pages, 14 figures, submitted to Phys. Rev.
Beyond the relativistic mean-field approximation (II): configuration mixing of mean-field wave functions projected on angular momentum and particle number
The framework of relativistic self-consistent mean-field models is extended
to include correlations related to the restoration of broken symmetries and to
fluctuations of collective variables. The generator coordinate method is used
to perform configuration mixing of angular-momentum and particle-number
projected relativistic wave functions. The geometry is restricted to axially
symmetric shapes, and the intrinsic wave functions are generated from the
solutions of the relativistic mean-field + Lipkin-Nogami BCS equations, with a
constraint on the mass quadrupole moment. The model employs a relativistic
point-coupling (contact) nucleon-nucleon effective interaction in the
particle-hole channel, and a density-independent -interaction in the
pairing channel. Illustrative calculations are performed for Mg,
S and Ar, and compared with results obtained employing the model
developed in the first part of this work, i.e. without particle-number
projection, as well as with the corresponding non-relativistic models based on
Skyrme and Gogny effective interactions.Comment: 37 pages, 10 figures, submitted to Physical Review
Relativistic QRPA calculation of muon capture rates
The relativistic proton-neutron quasiparticle random phase approximation
(PN-RQRPA) is applied in the calculation of total muon capture rates on a large
set of nuclei from C to Pu, for which experimental values are
available. The microscopic theoretical framework is based on the Relativistic
Hartree-Bogoliubov (RHB) model for the nuclear ground state, and transitions to
excited states are calculated using the PN-RQRPA. The calculation is fully
consistent, i.e., the same interactions are used both in the RHB equations that
determine the quasiparticle basis, and in the matrix equations of the PN-RQRPA.
The calculated capture rates are sensitive to the in-medium quenching of the
axial-vector coupling constant. By reducing this constant from its free-nucleon
value by 10% for all multipole transitions, the calculation
reproduces the experimental muon capture rates to better than 10% accuracy.Comment: 19 pages, 5 figures, submitted to Phys. Rev.
Charge Dynamics in Cuprate Superconductors
In this lecture we present some interesting issues that arise when the
dynamics of the charge carriers in the CuO planes of the high temperature
superconductors is considered. Based on the qualitative picture of doping, set
by experiments and some previous calculations, we consider the strength of
various inter and intra-cell charge transfer susceptibilities, the question of
Coulomb screening and charge collective modes. The starting point is the usual
p-d model extended by the long range Coulomb (LRC) interaction. Within this
model it is possible to examine the case in which the LRC forces frustrate the
electronic phase separation, the instability which is present in the model
without an LRC interaction. While the static dielectric function in such
systems is negative down to arbitrarily small wavevectors, the system is not
unstable. We consider the dominant electronic charge susceptibilities and
possible consequences for the lattice properties.Comment: 14 pages, 15 figures, latex, to be published in "From Quantum
Mechanics to Technology", Lecture Notes in Physics, Springe
Relativistic Random-Phase Approximation with density-dependent meson-nucleon couplings
The matrix equations of the relativistic random-phase approximation (RRPA)
are derived for an effective Lagrangian characterized by density-dependent
meson-nucleon vertex functions. The explicit density dependence of the
meson-nucleon couplings introduces rearrangement terms in the residual two-body
interaction, that are essential for a quantitative description of excited
states. Illustrative calculations of the isoscalar monopole, isovector dipole
and isoscalar quadrupole response of Pb, are performed in the fully
self-consistent RRPA framework, based on effective interactions with a
phenomenological density dependence adjusted to nuclear matter and ground-state
properties of spherical nuclei. The comparison of the RRPA results on multipole
giant resonances with experimental data constrains the parameters that
characterize the isoscalar and isovector channel of the density-dependent
effective interactions.Comment: RevTeX, 8 eps figures, submitted to Phys. Rev.
Magic numbers for superheavy nuclei in relativistic continuum Hartree-Bogoliubov theory
The magic proton and neutron numbers are searched in the superheavy region
with proton number =100 - 140 and neutron number = (+30) - (2+32)
by the relativistic continuum Hartree-Bogoliubov (RCHB) theory with
interactions NL1, NL3, NLSH, TM1, TW99, DD-ME1, PK1, and PK1R. Based on the
two-nucleon separation energies and , the two-nucleon gaps
and , the shell correction energies
and , the pairing energies and ,
and the pairing gaps and , =120, 132, and 138 and
=172, 184, 198, 228, 238, and 258 are suggested to be the magic numbers
within the present approach. The -decay half-lives are also discussed.
In addition, the potential energy surfaces of possible doubly magic nuclei are
obtained by the deformation-constrained relativistic mean field (RMF) theory,
and the shell effects stabilizing the nuclei are investigated. Furthermore, the
formation cross sections of 120 and 120 at the
optimal excitation energy are estimated by a phenomenological cold fusion
reactions model with the structure information extracted from the constrained
RMF calculation.Comment: 37 pages, 14 figure
Density dependent hadron field theory for neutron stars with antikaon condensates
We investigate and condensation in -equilibrated
hyperonic matter within a density dependent hadron field theoretical model. In
this model, baryon-baryon and (anti)kaon-baryon interactions are mediated by
the exchange of mesons. Density dependent meson-baryon coupling constants are
obtained from microscopic Dirac Brueckner calculations using Groningen and Bonn
A nucleon-nucleon potential. It is found that the threshold of antikaon
condensation is not only sensitive to the equation of state but also to
antikaon optical potential depth. Only for large values of antikaon optical
potential depth, condensation sets in even in the presence of negatively
charged hyperons. The threshold of condensation is always reached
after condensation. Antikaon condensation makes the equation of state
softer thus resulting in smaller maximum mass stars compared with the case
without any condensate.Comment: 20 pages, 7 figures; final version to appear in Physical Review
Modelization of the EOS
This article summarizes theoretical predictions for the density and isospin
dependence of the nuclear mean field and the corresponding nuclear equation of
state. We compare predictions from microscopic and phenomenological approaches.
An application to heavy ion reactions requires to incorporate these forces into
the framework of dynamical transport models. Constraints on the nuclear
equation of state derived from finite nuclei and from heavy ion reactions are
discussed.Comment: 17 pages, 13 figures, contributed paper to the World Consensus
Initiative (WCI) book "Dynamics and Thermodynamics with Nucleonic Degrees of
Freedom
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