1,599 research outputs found
Large-space shell-model calculations for light nuclei
An effective two-body interaction is constructed from a new Reid-like
potential for a large no-core space consisting of six major shells and is used
to generate the shell-model properties for light nuclei from =2 to 6. (For
practical reasons, the model space is partially truncated for =6.) Binding
energies and other physical observables are calculated and compare favorably
with experiment.Comment: prepared using LaTex, 21 manuscript pages, no figure
Exact Solutions of Model Hamiltonian Problems with Effective Interactions
We demonstrate with soluble models how to employ the effective Hamiltonian
approach of Lee and Suzuki to obtain all the exact eigenvalues of the full
Hamiltonian. We propose a new iteration scheme to obtain the effective
Hamiltonian and demonstrate its convergence properties.Comment: 12 pages and 1 figur
Propagator of a Charged Particle with a Spin in Uniform Magnetic and Perpendicular Electric Fields
We construct an explicit solution of the Cauchy initial value problem for the
time-dependent Schroedinger equation for a charged particle with a spin moving
in a uniform magnetic field and a perpendicular electric field varying with
time. The corresponding Green function (propagator) is given in terms of
elementary functions and certain integrals of the fields with a characteristic
function, which should be found as an analytic or numerical solution of the
equation of motion for the classical oscillator with a time-dependent
frequency. We discuss a particular solution of a related nonlinear Schroedinger
equation and some special and limiting cases are outlined.Comment: 17 pages, no figure
New calculations of the PNC Matrix Element for the 0 doublet in N
A new calculation of the predominantly isoscalar PNC matrix element between
the (E 8.7 MeV) states in N has
been carried out in a (0+1+2+3+4) model space with the
Warburton-Brown interaction. The magnitude of the PNC matrix element of 0.22 to
0.34 eV obtained with the DDH PNC interaction is substantially suppressed
compared with previous calculations in smaller model spaces but shows agreement
with the preliminary Seattle experimental data. The calculated sign is opposite
to that obtained experimentally, and the implications of this are discussed.Comment: REVTEX, 28 page
Photon-Photon Scattering, Pion Polarizability and Chiral Symmetry
Recent attempts to detect the pion polarizability via analysis of
measurements are examined. The connection
between calculations based on dispersion relations and on chiral perturbation
theory is established by matching the low energy chiral amplitude with that
given by a full dispersive treatment. Using the values for the polarizability
required by chiral symmetry, predicted and experimental cross sections are
shown to be in agreement.Comment: 21 pages(+10 figures available on request), LATEX, UMHEP-38
The Fall of Stringy de Sitter
Kachru, Kallosh, Linde, & Trivedi recently constructed a four-dimensional de
Sitter compactification of IIB string theory, which they showed to be
metastable in agreement with general arguments about de Sitter spacetimes in
quantum gravity. In this paper, we describe how discrete flux choices lead to a
closely-spaced set of vacua and explore various decay channels. We find that in
many situations NS5-brane meditated decays which exchange NSNS 3-form flux for
D3-branes are comparatively very fast.Comment: 35 pp (11 pp appendices), 5 figures, v3. fixed minor typo
An amplitude analysis of the reaction
A simple partial wave amplitude analysis of has been performed for data in the range p_{\sl lab} = 360 -- 1000
MeV/c. Remarkably few partial waves are required to fit the data, while the
number of required values barely changes over this energy range. However,
the resulting set of partial wave amplitudes is not unique. We discuss possible
measurements with polarized beam and target which will severely restrict and
help resolve the present analysis ambiguities. New data from the reaction
alone, are insufficient for that
purpose.Comment: 16 pages (revtex), 8 figures available on request, submitted to Phys.
Rev.
Magnetic properties of a new molecular-based spin-ladder system: (5IAP)2CuBr4*2H2O
We have synthesized and characterized a new spin-1/2 Heisenberg
antiferromagnetic ladder: bis 5-iodo-2-aminopyridinium tetrabromocuprate(II)
dihydrate. X-ray diffraction studies show the structure of the compound to
consist of well isolated stacked ladders and the interaction between the Cu(2+)
atoms to be due to direct Br...Br contacts. Magnetic susceptibility and
magnetization studies show the compound to be in the strong-coupling limit,
with the interaction along the rungs (J' ~ 13 K) much greater than the
interaction along the rails (J ~ 1 K). Magnetic critical fields are observed
near 8.3 T and 10.4 T, respectively, establishing the existence of the energy
gap.Comment: 10 pages, 4 figures, submitted to Phys. Rev. B Figure 4 did not
print. *.eps files replaced with figures.ps fil
Current and power spectrum in a magnetic tunnel device with an atomic size spacer
Current and its noise in a ferromagnetic double tunnel barrier device with a
small spacer particle were studied in the framework of the sequential tunneling
approach. Analytical formulae were derived for electron tunneling through the
spacer particle containing only a single energy level. It was shown that
Coulomb interactions of electrons with a different spin orientation lead to an
increase of the tunnel magnetoresistance. Interactions can also be responsible
for the negative differential resistance. A current noise study showed, which
relaxation processes can enhance or reduce fluctuations leading either to a
super-Poissonian or a sub-Poissonian shot noise.Comment: 12 pages, 4 figure
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