1,590,784 research outputs found
The Complex of Solutions of the Nested Bethe Ansatz. The A_2 Spin Chain
The full set of polynomial solutions of the nested Bethe Ansatz is
constructed for the case of A_2 rational spin chain. The structure and
properties of these associated solutions are more various then in the case of
usual XXX (A_1) spin chain but their role is similar
Adiabatic Motion of a Quantum Particle in a Two-Dimensional Magnetic Field
The adiabatic motion of a charged, spinning, quantum particle in a two -
dimensional magnetic field is studied. A suitable set of operators generalizing
the cinematical momenta and the guiding center operators of a particle moving
in a homogeneous magnetic field is constructed. This allows us to separate the
two degrees of freedom of the system into a {\sl fast} and a {\sl slow} one, in
the classical limit, the rapid rotation of the particle around the guiding
center and the slow guiding center drift. In terms of these operators the
Hamiltonian of the system rewrites as a power series in the magnetic length
\lb=\sqrt{\hbar c\over eB} and the fast and slow dynamics separates. The
effective guiding center Hamiltonian is obtained to the second order in the
adiabatic parameter \lb and reproduces correctly the classical limit.Comment: 17 pages, LaTe
GRS 1915+105 : Flares, QPOs and other events at 15 GHz
Monitoring with the Ryle Telescope at 15 GHz of the Galactic X-ray transient
source GRS 1915+105 has revealed a remarkable range of rapid and extended
flares which appear to be related to the X-ray emission as recorded by the RXTE
all-sky monitor. Quasi-periodic oscillations in the range 20 - 40 min have been
found and are probably related to oscillations in the soft X-ray flux.Comment: 2 pages. To be published in Proc. IAU164 : Radio emission from
Galactic and Extragalactic Compact Sources (Socorro, 1997
Semiflexible polymers under external fields confined to two dimensions
The non-equilibrium structural and dynamical properties of semiflexible
polymers confined to two dimensions are investigated by molecular dynamics
simulations. Three different scenarios are considered: The force-extension
relation of tethered polymers, the relaxation of an initially stretched
semiflexible polymer, and semiflexible polymers under shear flow. We find
quantitative agreement with theoretical predictions for the force-extension
relation and the time dependence of the entropically contracting polymer. The
semiflexible polymers under shear flow exhibit significant conformational
changes at large shear rates, where less stiff polymers are extended by the
flow, whereas rather stiff polymers are contracted. In addition, the polymers
are aligned by the flow, thereby the two-dimensional semiflexible polymers
behave similarly to flexible polymers in three dimensions. The tumbling times
display a power-law dependence at high shear rate rates with an exponent
comparable to the one of flexible polymers in three-dimensional systems.Comment: Accepted for publication in J. Chem. Phy
Asymptotic expansion of the solution of the steady Stokes equation with variable viscosity in a two-dimensional tube structure
The Stokes equation with the varying viscosity is considered in a thin tube
structure, i.e. in a connected union of thin rectangles with heights of order
and with bases of order 1 with smoothened boundary. An
asymptotic expansion of the solution is constructed: it contains some
Poiseuille type flows in the channels (rectangles) with some boundary layers
correctors in the neighborhoods of the bifurcations of the channels. The
estimates for the difference of the exact solution and its asymptotic
approximation are proved.Comment: 22 pages, 20 figure
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