 98651 J. Piasecki and Ch. Gruber
 >From the adiabatic piston to macroscopic motion
induced by fluctuations
(190K, LATeX)
Oct 16, 98

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Abstract. The controversial problem of the evolution of an isolated system with an
internal adiabatic wall is investigated with the use of a simple
microscopic model and the Boltzmann equation. In the case of two infinite
volume
onedimensional ideal fluids separated by a piston whose mass is equal to
the mass of the fluid particles we obtain a rigorous explicit stationary
nonequilibrium solution of the Boltzmann equation. It is shown that
at equal pressures on both sides of the piston, the temperature difference
induces a nonzero average velocity, oriented toward the region of higher
temperature. It thus turns out that despite the absence of macroscopic forces
the asymmetry of fluctuations results in a systematic macroscopic motion.
This remarkable effect is analogous to the dynamics of stochastic ratchets,
where fluctuations conspire with spatial anisotropy to generate directed
motion. However, a different mechanism is involved here. The relevance of
the discovered motion to the adiabatic piston problem is discussed.
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