34 research outputs found
The nuclear scissors mode within two approaches (Wigner function moments versus RPA)
Two complementary methods to describe the collective motion, RPA and Wigner
function moments method, are compared on an example of a simple model -
harmonic oscillator with quadrupole-quadrupole residual interaction. It is
shown that they give identical formulae for eigenfrequencies and transition
probabilities of all collective excitations of the model including the scissors
mode, which here is the subject of our special attention. The exact relation
between the variables of the two methods and the respective dynamical equations
is established. The normalization factor of the "synthetic" scissors state and
its overlap with physical states are calculated analytically. The orthogonality
of the spurious state to all physical states is proved rigorously.Comment: 39 page
A new type of nuclear collective motion - the spin scissors mode
The coupled dynamics of low lying modes and various giant resonances are
studied with the help of the Wigner Function Moments method on the basis of
Time Dependent Hartree-Fock equations in the harmonic oscillator model
including spin-orbit potential plus quadrupole-quadrupole and spin-spin
residual interactions. New low lying spin dependent modes are analyzed. Special
attention is paid to the spin scissors mode.Comment: 21 page
Orbital and spin scissors modes in superfluid nuclei
Nuclear scissors modes are considered in the frame of Wigner function moments
method generalized to take into account spin degrees of freedom and pair
correlations simultaneously. A new source of nuclear magnetism, connected with
counter-rotation of spins up and down around the symmetry axis (hidden angular
momenta), is discovered. Its inclusion into the theory allows one to improve
substantially the agreement with experimental data in the description of
energies and transition probabilities of scissors modes in rare earth nuclei.Comment: arXiv admin note: text overlap with arXiv:1301.251
Nuclear Scissors with Pairing and Continuity Equation
The coupled dynamics of the isovector and isoscalar giant quadrupole
resonances and low lying modes (including scissors) are studied with the help
of the Wigner Function Moments (WFM) method generalized to take into account
pair correlations. Equations of motion for collective variables are derived on
the basis of the Time Dependent Hartree-Fock-Bogoliubov (TDHFB) equations in
the harmonic oscillator model with quadrupole-quadrupole (QQ) residual
interaction and a Gaussian pairing force. Special care is taken of the
continuity equation.Comment: 28 pages, 3 figure
Electric state below nuclear scissors
The solution of time dependent Hartree-Fock-Bogoliubov equations by the
Wigner function moments method predicts four low-lying states. Three of
them are known as various scissors modes. Fourth state is disposed below all
scissors modes and has the electrical nature. It is found that it represents
one of three branches of state which can exist in spherical nuclei and
which is split %due to a deformation. in deformed nuclei. It is discovered,
that the antiferromagnetic properties of nuclei lead to the splitting of
states already at the zero deformation.Comment: 20 pages, 6 figures, 2 table
Nuclear Scissors Mode with Pairing
The coupled dynamics of the scissors mode and the isovector giant quadrupole
resonance are studied using a generalized Wigner function moments method taking
into account pair correlations. Equations of motion for angular momentum,
quadrupole moment and other relevant collective variables are derived on the
basis of the time dependent Hartree-Fock-Bogoliubov equations. Analytical
expressions for energy centroids and transitions probabilities are found for
the harmonic oscillator model with the quadrupole-quadrupole residual
interaction and monopole pairing force. Deformation dependences of energies and
values are correctly reproduced. The inclusion of pair correlations
leads to a drastic improvement in the description of qualitative and
quantitative characteristics of the scissors mode.Comment: 36 pages, 5 figures, the results of calculation by another method and
the section concerning currents are adde
Semirelativistic stability of N-boson systems bound by 1/r pair potentials
We analyze a system of self-gravitating identical bosons by means of a
semirelativistic Hamiltonian comprising the relativistic kinetic energies of
the involved particles and added (instantaneous) Newtonian gravitational pair
potentials. With the help of an improved lower bound to the bottom of the
spectrum of this Hamiltonian, we are able to enlarge the known region for
relativistic stability for such boson systems against gravitational collapse
and to sharpen the predictions for their maximum stable mass.Comment: 11 pages, considerably enlarged introduction and motivation,
remainder of the paper unchange
Toroidal quadrupole transitions associated to collective rotational-vibrational motions of the nucleus
In the frame of the algebraic Riemann Rotational Model one computes the
longitudinal, transverse and toroidal multipoles corresponding to the
excitations of low-lying levels in the ground state band of several even-even
nuclei by inelastic electron scattering (e,e'). Related to these transitions a
new quantity, which accounts for the deviations from the Siegert theorem, is
introduced. The intimate connection between the nuclear vorticity and the
dynamic toroidal quadrupole moment is underlined. Inelastic differential
cross-sections calculated at backscattering angles shows the dominancy of
toroidal form-factors over a broad range of momentum transfer.Comment: 11 pages in LaTex, 3 figures available by fax or mail, accepted for
publication in J.Phys.