281,419 research outputs found
A calculable and quasi-practical gas
A new kinetic approach is developed and a quasi-practical gas is defined to
which the new approach can be applied. One of the advantages of this new
approach over the standard one is direct calculability in terms of today's
computational means.Comment: 12 pages, 6 figures, late
Paradoxical aspects of the kinetic equations
Two paradoxical aspects of the prevailing kinetic equations are presented.
One is related to the usual understanding of distribution function and the
other to the usual understanding of the phase space. With help of simple
counterexamples and direct analyses, involved paradoxes manifest themselves.Comment: 9 pages, Late
A path-integral approach to the collisional Boltzmann gas
Collisional effects are included in the path-integral formulation that was
proposed in one of our previous paper for the collisionless Boltzmann gas. In
calculating the number of molecules entering a six-dimensional phase volume
element due to collisions, both the colliding molecules and the scattered
molecules are allowed to have distributions; thus the calculation is done
smoothly and no singularities arise.Comment: 18 pages, 11 figure
Mathematical investigation of the Boltzmann collisional operator
Problems associated with the Boltzmann collisional operator are unveiled and
discussed. By careful investigation it is shown that collective effects of
molecular collisions in the six-dimensional position and velocity space are
more sophisticated than they appear to be.Comment: 5 pages, 1 figure
Counterexamples of Boltzmann's equation
To test kinetic theories, simple and practical setups are proposed. It turns
out that these setups cannot be treated by Boltzmann's equation. An alternative
method, called the path-integral approach, is then employed and a number of
ready-for-verification results are obtained.Comment: 17 pages, 6 figures, theoretical analyses have been moved to
appendixe
A new uncertainty principle
By examining two counterexamples to the existing theory, it is shown, with
mathematical rigor, that as far as scattered particles are concerned the true
distribution function is in principle not determinable (indeterminacy principle
or uncertainty principle) while the average distribution function over each
predetermined finite velocity solid-angle element can be calculated.Comment: 12 pages, 7 figure
Boltzmann's H-theorem and time irreversibility
It is shown that the justification of the Boltzman H-theorem needs more than
just the assumption of molecular chaos and the picture of time irreversibility
related to it should be reinvestigated.Comment: 7 pages, 3 figures, changes in languag
Nonexistence of time reversibility in statistical physics
Contrary to the customary thought prevailing for long, the time reversibility
associated with beam-to-beam collisions does not really exist. Related facts
and consequences are presented. The discussion, though involving simple
mathematics and physics only, is well-related to the foundation of statistical
theory.Comment: 10 pages, 5 figures, late
A counterexample against the Vlasov equation
A simple counterexample against the Vlasov equation is put forward, in which
a magnetized plasma is perturbed by an electromagnetic standing wave.Comment: 5 pages, 1 figur
Paradoxes in the Boltzmann kinetic theory
Paradoxes in the Boltzmann kinetic theory are presented. Firstly, it is
pointed out that the usual notion concerning the perfect continuity of
distribution function is not generally valid; in many important situations
using certain types of discontinuous distribution functions is an absolute
must. Secondly, it is revealed that there is no time reversibility in terms of
beam-to-beam collisions and, in connection with this, there are intrinsic
difficulties in formulating the net change of molecular density due to
collisions, either in the three-dimensional velocity space or in the
six-dimensional phase space. With help of simple examples, the paradoxes
manifest themselves clearly.Comment: 18 pages, 10 figures, late
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