Entropy 2004, 6(1), 76-86; doi:10.3390/e6010076
Article

Modified Feynman ratchet with velocity-dependent fluctuations

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Received: 2 July 2003; Accepted: 10 December 2003 / Published: 15 March 2004
(This article belongs to the Special Issue Quantum Limits to the Second Law of Thermodynamics)
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract: The randomness of Brownian motion at thermodynamic equilibrium can be spontaneously broken by velocity-dependence of fluctuations, i.e., by dependence of values or probability distributions of fluctuating properties on Brownian-motional velocity. Such randomness-breaking can spontaneously obtain via interaction between Brownian-motional Doppler effects --- which manifest the required velocity-dependence --- and system geometrical asymmetry. A non random walk is thereby spontaneously superposed on Brownian motion, resulting in a systematic net drift velocity despite thermodynamic equilibrium. The time evolution of this systematic net drift velocity --- and of velocity probability density, force, and power output --- is derived for a velocity-dependent modification of Feynman's ratchet. We show that said spontaneous randomness-breaking, and consequent systematic net drift velocity, imply: bias from the Maxwellian of the system's velocity probability density, the force that tends to accelerate it, and its power output. Maximization, especially of power output, is discussed. Uncompensated decreases in total entropy, challenging the second law of thermodynamics, are thereby implied.
Keywords: second law of thermodynamics; spontaneous momentum flow; Feynman ratchet; velocity-dependent fluctuations; Doppler effect; nonrandom walk
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MDPI and ACS Style

Denur, J. Modified Feynman ratchet with velocity-dependent fluctuations. Entropy 2004, 6, 76-86.

AMA Style

Denur J. Modified Feynman ratchet with velocity-dependent fluctuations. Entropy. 2004; 6(1):76-86.

Chicago/Turabian Style

Denur, Jack. 2004. "Modified Feynman ratchet with velocity-dependent fluctuations." Entropy 6, no. 1: 76-86.

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