Classical fluids of negative heat capacity |
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Authors: | P T Landsberg R P Woodard |
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Institution: | (1) Faculty of Mathematical Studies, University of Southampton, SO9 5NH Southampton, UK;(2) Department of Physics, University of Florida, 32611 Gainesville, Florida |
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Abstract: | It is shown that new parametersX can be defined such that the heat capacity CxT(S/T)x is negative, even when the canonical ensemble i.e., at fixed T=(U/S)Y and YX] is stable. This implies an extension of the classical theory of polytropes from ideal gases to general fluids. As examples of negative heat capacity systems we treat blackbody radiation and general gas systems with nonsingular T. For the case of a simple ideal gas we even exhibit an apparatus which enforces a constraint X(p, V)=const that makes Cx<0. We then show that it is possible to infer the statistical mechanics of canonicallyunstable systems-for which even the traditional heat capacities are negative-by imposing constraints that stabilize the associated noncanonical ensembles. Two explicit models are discussed. |
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Keywords: | Heat capacity negative fluids classical blackbody radiation |
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