156 research outputs found
Critical Viscosity Exponent for Fluids: What Happend to the Higher Loops
We arrange the loopwise perturbation theory for the critical viscosity
exponent , which happens to be very small, as a power series in
itself and argue that the effect of loops beyond two is negligible.
We claim that the critical viscosity exponent should be very closely
approximated by .Comment: 9 pages and 3 figure
Growth Models and Models of Turbulence : A Stochastic Quantization Perspective
We consider a class of growth models and models of turbulence based on the
randomly stirred fluid. The similarity between the predictions of these models,
noted a decade earlier, is understood on the basis of a stochastic quantization
scheme.Comment: 3 page
Coupled non-equilibrium growth equations: Self-consistent mode coupling using vertex renormalization
We find that studying the simplest of the coupled non-equilibrium growth
equations of Barabasi by self-consistent mode coupling requires the use of
dressed vertices. Using the vertex renormalization, we find a roughness
exponent which already in the leading order is quite close to the numerical
value.Comment: 7 pages, 3 figure
Critical light scattering in liquids
We compare theoretical results for the characteristic frequency of the
Rayleigh peak calculated in one-loop order within the field theoretical method
of the renormalization group theory with experiments and other theoretical
results. Our expressions describe the non-asymptotic crossover in temperature,
density and wave vector. In addition we discuss the frequency dependent shear
viscosity evaluated within the same model and compare our theoretical results
with recent experiments in microgravity.Comment: 17 pages, 12 figure
Theory of Ferromagnetism in Diluted Magnetic Semiconductor Quantum Wells
We present a mean field theory of ferromagnetism in diluted magnetic
semiconductor quantum wells. When subband mixing due to exchange interactions
between quantum well free carriers and magnetic impurities is neglected,
analytic result can be obtained for the dependence of the critical temperature
and the spontaneous magnetization on the distribution of magnetic impurities
and the quantum well width. The validity of this approximate theory has been
tested by comparing its predictions with those from numerical self-consistent
field calculations. Interactions among free carriers, accounted for using the
local-spin-density approximation, substantially enhance the critical
temperature. We demonstrate that an external bias potential can tune the
critical temperature through a wide range.Comment: 4 pages, 3 figures, submitted to Phys. Rev.
Field Effect Magnetization Reversal in Ferromagnetic Semiconductor Quantum Wells
We predict that a novel bias-voltage assisted magnetization reversal process
will occur in Mn doped II-VI semiconductor quantum wells or heterojunctions
with carrier induced ferromagnetism. The effect is due to strong
exchange-coupling induced subband mixing that leads to electrically tunable
hysteresis loops. Our model calculations are based on the mean-field theory of
carrier induced ferromagnetism in Mn-doped quantum wells and on a
semi-phenomenological description of the host II-VI semiconductor valence
bands.Comment: 5 pages, 4 figure
Center or Limit Cycle: Renormalization Group as a Probe
Based on our studies done on two-dimensional autonomous systems, forced
non-autonomous systems and time-delayed systems, we propose a unified
methodology - that uses renormalization group theory - for finding out
existence of periodic solutions in a plethora of nonlinear dynamical systems
appearing across disciplines. The technique will be shown to have a non-trivial
ability of classifying the solutions into limit cycles and periodic orbits
surrounding a center. Moreover, the methodology has a definite advantage over
linear stability analysis in analyzing centers
Novel universality classes of coupled driven diffusive systems
Motivated by the phenomenologies of dynamic roughening of strings in random
media and magnetohydrodynamics, we examine the universal properties of driven
diffusive system with coupled fields. We demonstrate that cross-correlations
between the fields lead to amplitude-ratios and scaling exponents varying
continuosly with the strength of these cross-correlations. The implications of
these results for experimentally relevant systems are discussed.Comment: To appear in Phys. Rev. E (Rapid Comm.) (2003
Renormalization group and isochronous oscillations
We show how the condition of isochronicity can be studied for two dimensional
systems in the renormalization group (RG) context. We find a necessary
condition for the isochronicity of the Cherkas and another class of cubic
systems. Our conditions are satisfied by all the cases studied recently by
Bardet et al \cite{bard} and Ghose Choudhury and Guh
Fluctuation-dissipation relationship in chaotic dynamics
We consider a general N-degree-of-freedom dissipative system which admits of
chaotic behaviour. Based on a Fokker-Planck description associated with the
dynamics we establish that the drift and the diffusion coefficients can be
related through a set of stochastic parameters which characterize the steady
state of the dynamical system in a way similar to fluctuation-dissipation
relation in non-equilibrium statistical mechanics. The proposed relationship is
verified by numerical experiments on a driven double well system.Comment: Revtex, 23 pages, 2 figure
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