174 research outputs found
S-matrix studies of resonances in A=3,4,5,6, and 12 nucleon systems
Resonances of certain light nuclei are explored by studying the complex pole
structures of the scattering matrices. Among other results we predict the
existence of three-neutron and three-proton resonances, a small spin-orbit
splitting in the low-lying He-5 and Li-5 states and the nonexistence of the
soft dipole resonance in He-6.Comment: Talk given at the XVth International Conference on Few-Body Problems
in Physics (22-26 July, 1997, Groningen, The Netherlands). To be published in
the conference proceedings in Nucl. Phys. A. 5 pages with 2 figures. The
postscript file and more information are available at
http://qmc.lanl.gov/~csot
Effects of B-8 size on the low-energy Be7(p,gamma)B8 cross section
We calculate several "size-like" B-8 observables within the microscopic
three-cluster model and study their potential constraints on the zero-energy
astrophysical S_{17}(0) factor of the Be7(p,gamma)B8 reaction. We find within
our three-cluster model that a simultaneous reproduction of the experimental
data for the B-8 radius and quadrupole moment and of the B8-Li8 Coulomb
displacement energy implies S_{17}(0)=(23-25) eVb.Comment: 8 pages with 1 figure. The original version with further details and
more information are available at http://qmc.lanl.gov/~csot
Low-lying continuum structures in B8 and Li8 in a microscopic model
We search for low-lying resonances in the B8 and Li8 nuclei using a
microscopic cluster model and a variational scattering method, which is
analytically continued to complex energies. After fine-tuning the
nucleon-nucleon interaction to get the known 1+ state of B8 at the right
energy, we reproduce the known spectra of the studied nuclei. In addition, our
model predicts a 1+ state at 1.3 MeV in B8, relative to the Be7+p threshold,
whose corresponding pair is situated right at the Li7+n threshold in Li8.
Lacking any experimental evidence for the existence of such states, it is
presently uncertain whether these structures really exist or they are spurious
resonances in our model. We demonstrate that the predicted state in B8, if it
exists, would have important consequences for the understanding of the
astrophysically important Be7(p,gamma)B8 reaction.Comment: 6 pages with 1 figure. The postscript file and more information are
available at http://nova.elte.hu/~csot
Information technology in rural Hungary: plans and reality
Rural areas cover 87% of the territory and are inhabited by 45% of the population in Hungary. These areas have the same problem as most of the rural areas in Europe: migration of the active, well-trained labour force, depopulation, unfavourable age structure, high unemployment rate with critical labour market situation in the small settlements. Information and Communication Technology – if used properly – can serve as a solution to these problems, although there is much to be done in this field. The authors have started to examine the current situation of the basic ICT-indicators in Hungary, with a special focus on small settlements, and they have also given a historical overview on the past years’ governmental strategies (especially the National Information Society Strategy), the new National Rural Development Strategy and civic efforts (ex. The telecottage movement) to boost the widespread usage of these technologies, as well as an evaluation of the impact of the aforementioned factors
Large-space cluster model calculations for the He3(He3,2p)He4 and H3(H3,2n)He4 reactions
The He3(He3,2p)He4 and H3(H3,2n)He4 reactions are studied in a microscopic
cluster model. We search for resonances in the He3+He3 and He4+p+p channels
using methods that treat the two- and three-body resonance asymptotics
correctly. Our results show that the existence of a low-energy resonance or
virtual state, which could influence the Be-7 and B-8 solar neutrino fluxes, is
rather unlikely. Our calculated He3(He3,2p)He4 and H3(H3,2n)He4 cross sections
are in a good general agreement with the experimental data.Comment: 12 pages with 3 figures. The postscript file and more information are
available at http://nova.elte.hu/~csot
Pairing anti-halo effect
We discuss pairing correlations in weakly bound neutron rich nuclei, by using
the coordinate-space Hartree-Fock-Bogolyubov approach which allows to take
properly into account the coupling to particle continuum. We show that the
additional pairing binding energy acts against a development of an infinite rms
radius, even in situations when an l=0 single-particle orbital becomes unbound.Comment: 10 RevTeX pages, 3 EPS figure
Comment on ``Large-space shell-model calculations for light nuclei''
In a recent publication Zheng, Vary, and Barrett reproduced the negative
quadrupole moment of Li-6 and the low-lying positive-parity states of He-5 by
using a no-core shell model. In this Comment we question the meaning of these
results by pointing out that the model used is inadequate for the reproduction
of these properties.Comment: Latex with Revtex, 1 postscript figure in separate fil
Parity-violating alpha-decay of the 3.56-MeV J,T=0+,1 state of Li-6
We study the parity-violating alpha+d decay of the lowest 0+ state of Li-6 in
a microscopic three-cluster model. The initial bound and the final scattering
states are described consistently within the same model. The parity-violating
decay width is calculated in perturbation theory using the parity-nonconserving
nucleon-nucleon interaction of Desplanques, Donoghue, and Holstein (DDH). We
find that the decay width is sensitive to dynamical degrees of freedom which
are beyond the alpha+p+n model, for example, alpha excitation and breakup. In
our full model, which contains breathing excitations of the alpha particle and
H-3 + He-3 rearrangement, the parity-nonconserving decay width is
Gamma=3.97x10^{-9} eV, using the DDH coupling constants.Comment: LaTex with RevTe
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