Entropy 2004, 6[1], 50-56
ISSN 1099-4300

The adiabatic piston: a perpetuum mobile in the mesoscopic realm

Bruno Crosignani1,2, Paolo Di Porto2 and Claudio Conti3

1 Department of Applied Physics, California Institute of Technology, Pasadena, California 91125, USA.
E-mail: bcross@caltech.edu
2 Dipartimento di Fisica, Universitá dell'Aquila, 67010 L'Aquila, Italy
and Istituto Nazionale per la Fisica della Materia, Universitá di Roma "La Sapienza", 00185 Roma, Italy.
3 Istituto Nazionale per la Fisica della Materia, Universitá Roma Tre, 00146 Roma, Italy.

Received: 23 September 2003 / Accepted: 15 December 2003 / Published: 11 March 2004

Abstract: A detailed analysis of the adiabatic-piston problem reveals, for a finely-tuned choice of the spatial dimensions of the system, peculiar dynamical features that challenge the statement that an isolated system necessarily reaches a time-independent equilibrium state. In particular, the piston behaves like a perpetuum mobile, i.e., it never comes to a stop but keeps wandering, undergoing sizeable oscillations around the position corresponding to maximum entropy; this has remarkable implications on the entropy changes of a mesoscopic isolated system and on the limits of validity of the second law of thermodynamics in the mesoscopic realm.

Keywords: Brownian motors; perpetuum mobile; second law.

PACS codes: 05.70.-a, 05.40.-a, 05.20.-y

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