How Does Pressure Fluctuate in Equilibrium?
We study fluctuations of pressure in equilibrium for classical particle systems. In equilibrium statistical mechanics, pressure for a microscopic state is defined by the derivative of a thermodynamic function or, more mechanically, through the momentum current. We show that although the two expectation values converge to the same equilibrium value in the thermodynamic limit, the variance of the mechanical pressure is in general greater than that of the pressure defined through the thermodynamic relation. We also present a condition for experimentally detecting the difference between them in an idealized measurement of momentum transfer.
KeywordsThermodynamic fluctuation theory in equilibrium Pressure fluctuation Landau-Lifshitz fluctuation theory Classical statistical mechanics
The authors thank Yoshi Oono for his useful comments. The present work was supported by KAKENHI Nos. 25103002 and 17H01148.
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