IWNET12
IWNET12
Thermally induced non-equilibrium uctuations: gravity and nite-
size eects
Jan V. Sengers1, José M. Ortiz de Zárate2
1 Institute for Physical Science and Technology, University of Maryland, College Park, MD, USA
2 Departamento de Física Aplicada, Universidad Complutense, Madrid, Spain
Abstract
This lecture will be concerned with uctuations in uids in the presence of a temperature gradient. Non-
equilibrium uctuating hydrodynamics shows that such uctuations are always spatially long ranged due to
mode-coupling eects induced by the temperature gradient. The intensity of the non-equilibrium uctuations
is greatly enhanced compared to those in equilibrium and exhibits a dramatic dependence on the wavelength at
all length scales in the system. At small wavelengths the intensity of the non-equilibrium uctuations increases
with the 4th power of the wavelength. At larger wavelengths the uctuations become aected by gravity and
by nite-size eects.
We shall review how by supplementing light-scattering measurements with shadowgraph measurements experi-
mental information covering non-equilibrium uctuations at all relevant length scales has been obtained. Gravity
eects have been beautifully demonstrated recently by comparing earth-bound experiments with experiments
in a satellite [1].
References
[1] C.J. Takacs, A. Vailati, R. Cerbino, S. Mazzoni, M. Giglio, and D.S. Cannell, Phys. Rev. Lett. 106, 244502
(2011).
E-mail: sengers@umd.edu

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