Deviations from Linear Theory for Fluctuations below the Supercritical Primary Bifurcation to Electroconvection

Titelangaben

Scherer, Michael A. ; Ahlers, Guenter ; Hörner, Frank ; Rehberg, Ingo:
Deviations from Linear Theory for Fluctuations below the Supercritical Primary Bifurcation to Electroconvection.
In: Physical Review Letters. Bd. 85 (Oktober 2000) Heft 18 . - S. 3754-3757.
ISSN 1079-7114
DOI der Verlagsversion: https://doi.org/10.1103/PhysRevLett.85.3754

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Abstract

Over two decades ago it was predicted that nonlinear interactions between thermally driven fluctuations in dissipative nonlinear nonequilibrium systems lead to deviations from mean-field theory. Here we report experimental observations of such deviations as a supercritical primary bifurcation is approached. We measured the mean-square director-angle fluctuations ‹θ²› below the bifurcation to electroconvection of two different nematic liquid crystals. For ε{mf}≡V²/V{c,mf}² - 1 ≲ - 0.1 (V is the applied voltage) we find ‹θ²› α|ε{mf}|⁻γ with γ given by linear theory (LT). Closer to the bifurcation there are deviations from LT with a smaller γ and with V² > V{c,mf}².