title: Toy model of hydrodynamic fluctuations.
abstract: We study hydrodynamic fluctuations in an ideal gas. Because one is interested in thermodynamic properties of small volume elements, Einstein's theory of equilibrium fluctuations in large systems is insufficient. A toy model of correlated fluctuations in neighboring small cells leads us to the distinction of biased and unbiased momentum densities. Hydrodynamic equations that satisfy the fluctuation-dissipation theorem can then be formulated in terms of these two different momentum densities or velocities.
authors.affiliation: Department of Materials, Polymer Physics, ETH Zürich, HCI H 543, CH-8093 Zürich, Switzerland. hco@mat.ethz.ch
authors.forename: Hans Christian
authors.initials: HC
authors.lastname: Ottinger