https://doi.org/10.1140/epjb/e2002-00246-2
Non-equilibrium behavior at a liquid-gas critical point
1
Hahn-Meitner Institut, Abt. SF5, Glienicker Str. 100, 14109 Berlin,
Germany
2
Physics Department, Virginia Polytechnic Institute and
State University, Blacksburg, VA 24061-0435, USA
Corresponding authors: a santos@hmi.de - b tauber@vt.edu
Received:
4
April
2002
Published online:
13
August
2002
Second-order phase transitions in a non-equilibrium liquid-gas
model with reversible mode couplings, i.e., model H for binary-fluid
critical dynamics, are studied using dynamic field theory and the
renormalization group. The system is driven out of equilibrium
either by considering different values for the noise strengths in
the Langevin equations describing the evolution of the dynamic
variables (effectively placing these at different temperatures),
or more generally by allowing for anisotropic noise strengths, i.e.,
by constraining the dynamics to be at different temperatures in
- and
-dimensional subspaces, respectively.
In the first, isotropic case, we find one infrared-stable and
one unstable renormalization group fixed point. At the stable fixed
point, detailed balance is dynamically restored, with the two noise
strengths becoming asymptotically equal. The ensuing critical
behavior is that of the standard equilibrium model H. At the novel
unstable fixed point, the temperature ratio for the dynamic variables
is renormalized to infinity, resulting in an effective decoupling
between the two modes. We compute the critical exponents at this new
fixed point to one-loop order. For model H with spatially
anisotropic noise, we observe a critical softening only in the
-dimensional sector in wave vector space with lower noise
temperature. The ensuing effective two-temperature model H does not
have any stable fixed point in any physical dimension, at least to
one-loop order. We obtain formal expressions for the novel critical
exponents in a double expansion about the upper critical dimension
and with respect to
, i.e.,
about the equilibrium theory.
PACS: 64.60.Ht – Dynamic critical phenomena / 05.70.Ln – Non-equilibrium thermodynamics, irreversible processes / 64.60.Ak – Renormalization-group, fractal, and percolation studies of phase transitions
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2002