1,098 research outputs found
Effective-Mass Klein-Gordon-Yukawa Problem for Bound and Scattering States
Bound and scattering state solutions of the effective-mass Klein-Gordon
equation are obtained for the Yukawa potential with any angular momentum
. Energy eigenvalues, normalized wave functions and scattering phase
shifts are calculated as well as for the constant mass case. Bound state
solutions of the Coulomb potential are also studied as a limiting case.
Analytical and numerical results are compared with the ones obtained before.Comment: 13 pages, 1 figur
3D Finite Volume Simulation of Accretion Discs with Spiral Shocks
We perform 2D and 3D numerical simulations of an accretion disc in a close
binary system using the Simplified Flux vector Splitting (SFS) finite volume
method. In our calculations, gas is assumed to be the ideal one, and we
calculate the cases with gamma=1.01, 1.05, 1.1 and 1.2. The mass ratio of the
mass losing star to the mass accreting star is unity. Our results show that
spiral shocks are formed on the accretion disc in all cases. In 2D calculations
we find that the smaller gamma is, the more tightly the spiral winds. We
observe this trend in 3D calculations as well in somewhat weaker sense.Comment: 2 pages, LaTeX with 2 ps figures using crckapb.sty. To appear in the
Proceedings of Numerical Astrophysics 1998, Tokyo, Japan, 10-13 March, 1998,
eds. S. M. Miyama, K. Tomisaka and T. Hanawa (Kluwer Academic Publishers
Hadron-hadron interaction from SU(2) lattice QCD
We evaluate interhadron interactions in two-color lattice QCD from
Bethe-Salpeter amplitudes on the Euclidean lattice. The simulations are
performed in quenched SU(2) QCD with the plaquette gauge action at and the Wilson quark action. We concentrate on S-wave scattering states
of two scalar diquarks. Evaluating different flavor combinations with various
quark masses, we try to find out the ingredients in hadronic interactions.
Between two scalar diquarks (, the lightest baryon in SU(2)
system), we observe repulsion in short-range region, even though present quark
masses are not very light. We define and evaluate the "quark-exchange part" in
the interaction, which is induced by adding quark-exchange diagrams, or
equivalently, by introducing Pauli blocking among some of quarks. The repulsive
force in short-distance region arises only from the "quark-exchange part", and
disappears when quark-exchange diagrams are omitted. We find that the strength
of repulsion grows in light quark-mass regime and its quark-mass dependence is
similar to or slightly stronger than that of the color-magnetic interaction by
one-gluon-exchange (OGE) processes. It is qualitatively consistent with the
constituent-quark model picture that a color-magnetic interaction among quarks
is the origin of repulsion. We also find a universal long-range attractive
force, which enters in any flavor channels of two scalar diquarks and whose
interaction range and strength are quark-mass independent. The weak quark-mass
dependence of interaction ranges in each component implies that meson-exchange
contributions are small and subdominant, and the other contributions, {\it ex.}
flavor exchange processes, color-Coulomb or color-magnetic interactions, are
considered to be predominant, in the quark-mass range we evaluated.Comment: 14 pages, 20 figure
Spiral Structure in IP Peg: Confronting Theory and Observations
The first convincing piece of evidence of spiral structure in the accretion
disc in IP Pegasi was found by Steeghs et al. (1997). We performed two kinds of
2D hydrodynamic simulations, a SFS finite volume scheme and a SPH scheme, with
a mass ratio of 0.5. Both results agreed well with each other. We constructed
Doppler maps and line flux-binary phase relations based on density
distributions, the results agreeing well with those obtained by observation.Comment: 4 pages, LaTeX with 2 ps figures using crckapb.sty. To appear in the
Proceedings of Numerical Astrophysics 1998, Tokyo, Japan, 10-13 March, 1998,
eds. S. M. Miyama, K. Tomisaka and T. Hanawa (Kluwer Academic Publishers
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