57,065 research outputs found
Three-Body Scattering Below Breakup Threshold: An Approach without using Partial Waves
The Faddeev equation for three-body scattering below the three-body breakup
threshold is directly solved without employing a partial wave decomposition. In
the simplest form it is a three-dimensional integral equation in four
variables. From its solution the scattering amplitude is obtained as function
of vector Jacobi momenta. Based on Malfliet-Tjon type potentials differential
and total cross sections are calculated. The numerical stability of the
algorithm is demonstrated and the properties of the scattering amplitude
discussed.Comment: 21 pages, 7 figures included, uses psfig, revised versio
Lubich convolution quadratures and their application to problems described by space-time BIEs
Model Study of Three-Body Forces in the Three-Body Bound State
The Faddeev equations for the three-body bound state with two- and three-body
forces are solved directly as three-dimensional integral equation. The
numerical feasibility and stability of the algorithm, which does not employ
partial wave decomposition is demonstrated. The three-body binding energy and
the full wave function are calculated with Malfliet-Tjon-type two-body
potentials and scalar Fujita-Miyazawa type three-body forces. The influence of
the strength and range of the three-body force on the wave function, single
particle momentum distributions and the two-body correlation functions are
studied in detail. The extreme case of pure three-body forces is investigated
as well.Comment: 25 pages, 15 postscript figure
Two-dimensional behavior of the sublattice magnetization in three-dimensional Ising antiferromagnets
A three-dimensional layered Ising-Antiferromagnet with a ferromagnetic
intra-layer coupling to z neighbors, zJ > 0, and an antiferromagnetic
interlayer coupling to z' neighbors, z'J' < 0, is investigated by Monte Carlo
simulations on a hexagonal lattice. The physical nature of the anomalous
temperature bahavior of the sublattice magnetizations, which is found for
certain values of r=zJ/z'J' and z' in magnetic fields is explained in terms of
successive phase transitions. They take place on the ferromagnetic
2-dimensional spin-down sublattice at T = T_c^{2d}, smeared by a finite
stabilizing molecular field, and on both antiferromagnetically coupled
sublattices at T_c^{3d} > T_c^{2d}.Comment: 8 pages (TeX), 6 figures (eps), submitted to World Scientific:
Proceedings SDHS'99 Duisbur
Three-Body Scattering without Partial Waves
The Faddeev equation for three-body scattering at arbitrary energies is
formulated in momentum space and directly solved in terms of momentum vectors
without employing a partial wave decomposition. In its simplest form the
Faddeev equation for identical bosons is a three-dimensional integral equation
in five variables, magnitudes of relative momenta and angles. The elastic
differential cross section, semi-exclusive d(N,N') cross sections and total
cross sections of both elastic and breakup processes in the intermediate energy
range up to about 1 GeV are calculated based on a Malfliet-Tjon type potential,
and the convergence of the multiple scattering series is investigated in every
case. In general a truncation in the first or second order in the two-body
t-matrix is quite insufficient.Comment: 3 pages, Oral Contribution to the 19th European Few-Body Conference,
Groningen Aug. 23-27, 200
Two-Body T-Matrices without Angular Momentum Decomposition: Energy and Momentum Dependencies
The two-body t-matrix is calculated directly as function of two vector
momenta for different Malfliet-Tjon type potentials. At a few hundred MeV
projectile energy the total amplitude is quite a smooth function showing only a
strong peak in forward direction. In contrast the corresponding partial wave
contributions, whose number increases with increasing energy, become more and
more oscillatory with increasing energy. The angular and momentum dependence of
the full amplitude is studied and displayed on as well as off the energy shell
as function of positive and negative energies. The behavior of the t-matrix in
the vicinity of bound state poles and resonance poles in the second energy
sheet is studied. It is found that the angular dependence of T exhibits a very
characteristic behavior in the vicinity of those poles, which is given by the
Legendre function corresponding to the quantum number either of the bound state
or the resonance (or virtual) state. This behavior is illustrated with
numerical examples.Comment: 19 pages (revtex), 15 figure
Resonance Model for N Scattering and -Meson Production in the s Channel
A model for N scattering and -meson production in the S
channel is presented. The model includes N-scattering Born terms as well
as the N{} resonances S(1535) and S(1610). The -matrix is
computed in the -matrix approximation. The parameters of the model are
determined by fitting the elastic N-scattering -matrix to empirical
data. We find an excellent fit for all energies up to = 1.75 GeV.
Furthermore, a good description of the cross section for is obtained without further adjustment of parameters.Comment: LaTex 10 pages, 4 figures (not included;the postscript-figures are
available from [email protected] in subdirectory pub/sauerman, files:
fig1.ps, fig2.ps,fig3.ps,fig4.ps- or contact the authors via e-mail),
GSI-94-4
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