4,474 research outputs found
Non-equilibrium concentration fluctuations in binary liquids with realistic boundary conditions
Because of the spatially long-ranged nature of spontaneous fluctuations in
thermal non-equilibrium systems, they are affected by boundary conditions for
the fluctuating hydrodynamic variables. In this paper we consider a liquid
mixture between two rigid and impervious plates with a stationary concentration
gradient resulting from a temperature gradient through the Soret effect. For
liquid mixtures with a large Lewis number, we are able to obtain explicit
analytical expressions for the intensity of the non-equilibrium concentration
fluctuations as a function of the frequency and the wave number of
the fluctuations. In addition we elucidate the spatial dependence of the
intensity of the non-equilibrium fluctuations responsible for a non-equilibrium
Casimir effect.Comment: 9 pages, 2 figure
Local versus Nonlocal Order Parameter Field Theories for Quantum Phase Transitions
General conditions are formulated that allow to determine which quantum phase
transitions in itinerant electron systems can be described by a local
Landau-Ginzburg-Wilson or LGW theory solely in terms of the order parameter. A
crucial question is the degree to which the order parameter fluctuations couple
to other soft modes. Three general classes of zero-wavenumber order parameters,
in the particle-hole spin-singlet and spin-triplet channels, and in the
particle-particle channel, respectively, are considered. It is shown that the
particle-hole spin-singlet class does allow for a local LGW theory, while the
other two classes do not. The implications of this result for the critical
behavior at various quantum phase transitions are discussed, as is the
connection with nonanalyticities in the wavenumber dependence of order
parameter susceptibilities in the disordered phase.Comment: 9 pp., LaTeX, no figs, final version as publishe
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