Compressible dynamics, time-reversibility, Maxwell's demon, and the second law.

Panayotis A. Skordos

A tantalizing version of Maxwell's demon is presented which appears to operate reversibly. Our settup consists of a container of hard core disks which is separated into two parts by a membrane. The membrane selects which disk can penetrate depending on the disk's angle of incidence. Analysis of this system shows that the second law of thermodynamics requires the incompressibility of microscopic dynamics or an appropriate energy cost for compressible microscopic dynamics.

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