264 research outputs found
Generalized Kinetic Theory of Electrons and Phonons
A Generalized Kinetic Theory was proposed in order to have the possibility to
treat particles which obey a very general statistics. By adopting the same
approach, we generalize here the Kinetic Theory of electrons and phonons.
Equilibrium solutions and their stability are investigated.Comment: Proceedings of the International School and Workshop on Nonextensive
Thermodynamics and Physical Applications, NEXT 2001, 23-30 May 2001, Cagliari
(Italy) (To appear in Physica A
Vibrating quantum billiards on Riemannian manifolds
Quantum billiards provide an excellent forum for the analysis of quantum
chaos. Toward this end, we consider quantum billiards with time-varying
surfaces, which provide an important example of quantum chaos that does not
require the semiclassical () or high quantum-number
limits. We analyze vibrating quantum billiards using the framework of
Riemannian geometry. First, we derive a theorem detailing necessary conditions
for the existence of chaos in vibrating quantum billiards on Riemannian
manifolds. Numerical observations suggest that these conditions are also
sufficient. We prove the aforementioned theorem in full generality for one
degree-of-freedom boundary vibrations and briefly discuss a generalization to
billiards with two or more degrees-of-vibrations. The requisite conditions are
direct consequences of the separability of the Helmholtz equation in a given
orthogonal coordinate frame, and they arise from orthogonality relations
satisfied by solutions of the Helmholtz equation. We then state and prove a
second theorem that provides a general form for the coupled ordinary
differential equations that describe quantum billiards with one
degree-of-vibration boundaries. This set of equations may be used to illustrate
KAM theory and also provides a simple example of semiquantum chaos. Moreover,
vibrating quantum billiards may be used as models for quantum-well
nanostructures, so this study has both theoretical and practical applications.Comment: 23 pages, 6 figures, a few typos corrected. To appear in
International Journal of Bifurcation and Chaos (9/01
Decoherence Effects in Reactive Scattering
Decoherence effects on quantum and classical dynamics in reactive scattering
are examined using a Caldeira-Leggett type model. Through a study of dynamics
of the collinear H+H2 reaction and the transmission over simple one-dimensional
barrier potentials, we show that decoherence leads to improved agreement
between quantum and classical reaction and transmission probabilities,
primarily by increasing the energy dispersion in a well defined way. Increased
potential nonlinearity is seen to require larger decoherence in order to attain
comparable quantum-classical agreement.Comment: 25 pages, 6 figures, to be published in J. Chem. Phy
Minimum of and the phase transition of the Linear Sigma Model in the large-N limit
We reexamine the possibility of employing the viscosity over entropy density
ratio as a diagnostic tool to identify a phase transition in hadron physics to
the strongly coupled quark-gluon plasma and other circumstances where direct
measurement of the order parameter or the free energy may be difficult.
It has been conjectured that the minimum of eta/s does indeed occur at the
phase transition. We now make a careful assessment in a controled theoretical
framework, the Linear Sigma Model at large-N, and indeed find that the minimum
of eta/s occurs near the second order phase transition of the model due to the
rapid variation of the order parameter (here the sigma vacuum expectation
value) at a temperature slightly smaller than the critical one.Comment: 22 pages, 19 figures, v2, some references and several figures added,
typos corrected and certain arguments clarified, revised for PR
The Nonlinear Permittivity Including Non-Abelian Self-interaction of Plasmons in Quark-Gluon Plasma
By decomposing the distribution functions and color field to regular and
fluctuation parts, the solution of the semi-classical kinetic equations of
quark-gluon plasma is analyzed. Through expanding the kinetic equations of the
fluctuation parts to third order, the nonlinear permittivity including the
self-interaction of gauge field is obtained and a rough numerical estimate is
given out for the important \vk =0 modes of the pure gluon plasma.Comment: 7 pages, shortened version accepted by Chin.Phys.Let
Quantum Mechanics without an Equation of Motion
We propose a formulation of quantum mechanics in three dimensions with
spherical symmetry for a finite level system whose dynamics is not governed by
a differential equation of motion. The wavefunction is written as an infinite
sum in a complete set of square integrable functions. Interaction in the theory
is introduced in function space by a real finite tridiagonal symmetric matrix.
Information about the structure and dynamics of the system is contained in the
scattering matrix, which is defined in the usual way.Comment: 7 pages, 2 figures, and 3 table
Bose-Einstein Condensate Driven by a Kicked Rotor in a Finite Box
We study the effect of different heating rates of a dilute Bose gas confined
in a quasi-1D finite, leaky box. An optical kicked-rotor is used to transfer
energy to the atoms while two repulsive optical beams are used to confine the
atoms. The average energy of the atoms is localized after a large number of
kicks and the system reaches a nonequilibrium steady state. A numerical
simulation of the experimental data suggests that the localization is due to
energetic atoms leaking over the barrier. Our data also indicates a correlation
between collisions and the destruction of the Bose-Einstein condensate
fraction.Comment: 7 pages, 8 figure
MAGNETIC DETERMINATION OF IMPURITIES IN URANIUM FUEL SLUGS
A technique has been devised for the non-destructive determination of the uranium hydride and/or iron content in uranium fuel slugs of Hanford size. The technique, an adaptation of the Gouy method for measuring magnetic susceptibilities, is based on the ferromagnetic properties of the hydride below 173 deg K. A large electromagnet and a pain balance are utilized in measuring the magnetic forces on a vertically suspended slug at liquid nitrogen temperatures and at room temperature. It was found possible to test as many as 250 slugs per eight-hour day in this manner. (auth
Time parameterization and stationary distributions in a relativistic gas
In this paper we consider the effect of different time parameterizations on
the stationary velocity distribution function for a relativistic gas. We
clarify the distinction between two such distributions, namely the J\"{u}ttner
and the modified J\"{u}ttner distributions. Using a recently proposed model of
a relativistic gas, we show that the obtained results for the proper-time
averaging does not lead to modified J\"{u}ttner distribution (as recently
conjectured), but introduces only a Lorentz factor to the well-known
J\"{u}ttner function which results from observer-time averaging. We obtain
results for rest frame as well as moving frame in order to support our claim.Comment: 5 pages, 2 figure
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