Phase Space Portraits of an Unresolved Gravitational Maxwell Demon

In 1885, during initial discussions of J. C. Maxwell's celebrated thermodynamic demon, Whiting ⁽¹⁾ observed that the demon-like velocity selection of molecules can occur in a gravitationally bound gas. Recently, a gravitational Maxwell demon has been proposed which makes use of this observation D. P. Sheehan, J. Glick, and J. D. Means, Found. Phys. 30, 1227 (2000)]. Here we report on numerical simulations that detail its microscopic phase space structure. Results verify the previously hypothesized mechanism of its paradoxical behavior. This system appears to be the only example of a fully classical mechanical Maxwell demon that has not been resolved in favor of the second law of thermodynamics.