MPEJ Volume 10, No. 2, 18 pp.
Received: Jan 5, 2004. Revised: Feb 10, 2004. Accepted: Feb 10, 2004.

N. Chernov
On a slow drift of a massive piston in an ideal gas that remains at
mechanical equilibrium

ABSTRACT: We consider a heavy piston in an infinite cylinder
surrounded by ideal gases on both sides. The piston moves under
elastic collisions with gas atoms. We assume here that the gases
always exert equal pressures on the piston, hence the piston remains
at the so called mechanical equilibrium. However, the temperatures and
densities of the gases may differ across the piston. In that case some
earlier studies by Gruber, Piasecki and others reveal a very slow
motion (drift) of the piston in the direction of the hotter gas. At
the same time the energy is slowly transferred across the piston from
the hotter gas to the cooler one. While the previous studies of this
interesting phenomenon were only heuristic or experimental, we provide
first rigorous proofs assuming that the velocity distribution of the
ideal gas satisfies a certain ``cutoff'' condition.


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