634 research outputs found
Energy gaps and roton structure above the nu=1/2 Laughlin state of a rotating dilute Bose-Einstein condensate
Exact diagonalization study of a rotating dilute Bose-Einstein condensate
reveals that as the first vortex enters the system the degeneracy of the
low-energy yrast spectrum is lifted and a large energy gap emerges. As more
vortices enter with faster rotation, the energy gap decreases towards zero, but
eventually the spectrum exhibits a rotonlike structure above the nu=1/2
Laughlin state without having a phonon branch despite the short-range nature of
the interaction.Comment: 4 pages, 4 figures, 1 tabl
Interplay between isoscalar and isovector correlations in neutron-rich nuclei
The interplay between isoscalar and isovector correlations in the 1
states in neutron-rich (NZ) even-even nuclei is studied, taking examples
of the nuclei, O and O. The excitation
modes explored are isovector dipole and isoscalar compression dipole modes. The
self-consistent Hartree-Fock plus the random-phase approximation with the
Skyrme interaction, SLy4, is solved in coordinate space so as to take properly
into account the continuum effect. The isovector peak induced by isoscalar
correlation, the isoscalar peak induced by isovector correlation, and the
possible collective states made by both isoscalar and isovector correlations,
("iS-iV pigmy resonance"), are shown. The strong neutron-proton interaction in
nuclei can be responsible for controlling the isospin structure of normal
modes. It is explicitly shown that in the scattering by isoscalar (isovector)
particles on NZ even-even nuclei isovector (isoscalar) strength in
addition to isoscalar (isovector) strength may be populated.Comment: 20 pages,7 figure
Kinetic energy and spin-orbit splitting in nuclei near neutron drip line
Two important ingredients of nuclear shell-structure, kinetic energy and
spin-orbit splitting, are studied as a function of orbital angular momenta \ell
and binding energies, when binding energies of neutrons decrease towards zero.
If we use the standard parameters of the Woods-Saxon potential in \beta stable
nuclei and approach the limit of zero binding energy from 10 MeV, the
spin-orbit splitting for n=1 orbitals decreases considerably for \ell=1, while
for \ell > 2 little decreasing is observed in the limit. In contrast, the
kinetic energy decreases considerably for \ell \simleq 3. The smaller the \ell
values of orbitals, the larger the decreasing rate of both kinetic energy and
spin-orbit splitting. The dependence of the above bservation on the diffuseness
of potentials is studied.Comment: 12 pages, 3 figures, submitted to Nucl. Phy
A microscopic investigation of the transition form factor in the region of collective multipole excitations of stable and unstable nuclei
We have used a self-consistent Skyrme-Hartree-Fock plus Continuum-RPA model
to study the low-multipole response of stable and neutron/proton-rich Ni and Sn
isotopes. We focus on the momentum-transfer dependence of the strength
distribution, as it provides information on the structure of excited nuclear
states and in particular on the variations of the transition form factor (TFF)
with the energy. Our results show, among other things, that the TFF may show
significant energy dependence in the region of the isoscalar giant monopole
resonance and that the TFF corresponding to the threshold strength in the case
of neutron-rich nuclei is different compared to the one corresponding to the
respective giant resonance. Perspectives are given for more detailed future
investigations.Comment: 13 pages, incl. 9 figures; to appear in J.Phys.G,
http://www.iop.org/EJ/jphys
The Yrast Spectra of Weakly Interacting Bose-Einstein Condensates
The low energy quantal spectrum is considered as a function of the total
angular momentum for a system of weakly interacting bosonic atoms held together
by an external isotropic harmonic potential. It is found that besides the usual
condensation into the lowest state of the oscillator, the system exhibits two
additional kinds of condensate and associated thermodynamic phase transitions.
These new phenomena are derived from the degrees of freedom of "partition
space" which describes the multitude of different ways in which the angular
momentum can be distributed among the atoms while remaining all the time in the
lowest state of the oscillator
Phytohaemagglutinin on maternal and umbilical leukocytes
Almost all the umbilical lymphocytes showed more extensive blast cell formation
than that of their mother's lymphocytes with PHA. Pathological conditions of mother in pregnancy and labor such as anemia, gestational toxicosis,
difficult labor and asphyxia of babies, inhibited the normal response of both maternal and umbilical lymphocytes to PHA.</p
Change of shell structure and magnetic moments of odd-N deformed nuclei towards neutron drip line
Examples of the change of neutron shell-structure in both weakly-bound and
resonant neutron one-particle levels in nuclei towards the neutron drip line
are exhibited. It is shown that the shell-structure change due to the weak
binding may lead to the deformation of those nuclei with the neutron numbers 8, 20, 28 and 40, which are known to be magic numbers in stable
nuclei. Nuclei in the "island of inversion" are most easily and in a simple
manner understood in terms of deformation. As an example of spectroscopic
properties other than single-particle energies, magnetic moments of some
weakly-bound possibly deformed odd-N nuclei with neutron numbers close to those
traditional magic numbers are given, which are calculated using the wave
function of the last odd particle in deformed Woods-Saxon potentials.Comment: 21 pages, 6 figure
Low-Lying Excitations from the Yrast Line of Weakly Interacting Trapped Bosons
Through an extensive numerical study, we find that the low-lying,
quasi-degenerate eigenenergies of weakly-interacting trapped N bosons with
total angular momentum L are given in case of small L/N and sufficiently small
L by E = L hbar omega + g[N(N-L/2-1)+1.59 n(n-1)/2], where omega is the
frequency of the trapping potential and g is the strength of the repulsive
contact interaction; the last term arises from the pairwise repulsive
interaction among n octupole excitations and describes the lowest-lying
excitation spectra from the Yrast line. In this case, the quadrupole modes do
not interact with themselves and, together with the octupole modes, exhaust the
low-lying spectra which are separated from others by N-linear energy gaps.Comment: 5 pages, RevTeX, 2 figures, revised version, submitted to PR
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