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Entropy and irreversibility in a dilute gas of hard disks


The partition of the canonical entropy (invariant of motion) into a thermodynamic part 5th and a nonthermodynamic oneS nonth, respectively increasing and decreasing functions of time for a system approaching equilibrium, was proposed by Prigogine and co-workers. This viewpoint is critically examined in the special case of an initially uncorrelated gas of hard disks. BothSth and the leading term ofS nonth are evaluated for finite assemblies of 400,1600, and 6400 disks, by the method of molecular dynamics. There is good evidence that, in the limit of an infinite system, the Prigogine scheme is verified.

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On leave of absence from the University of Brussels, Belgium.

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Orban, J., Bellemans, A. Entropy and irreversibility in a dilute gas of hard disks. J Stat Phys 1, 467–474 (1969).

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Key words

  • entropy
  • irreversibility
  • method of molecular dynamics
  • gas of hard disks
  • H-function of Boltzmann