Experimental evidence of non-Gaussian fluctuations near a critical point.

Sylvain Joubaud (1) , Artem Petrosyan (1) , Sergio Ciliberto (1) , Nicolas B. Garnier (1)

1 Phys-ENS - Laboratoire de Physique de l'ENS Lyon

The orientation fluctuations of the director of a liquid crystal are measured, by a sensitive polarization interferometer, close to the Fréedericksz transition, which is a second order transition driven by an electric field. We show that near the critical value of the field the spatially averaged order parameter has a generalized Gumbel distribution instead of a Gaussian one. The latter is recovered away from the critical point. The relevance of slow modes is pointed out. The parameter of generalized Gumbel is related to the effective number of degrees of freedom.

Mots clés: phase transition; non-Gaussian fluctuations; critical point; finite size

Domaines: Mécanique statistique [cond-mat.stat-mech]; Matière Molle [cond-mat.soft]; Physique Générale [physics.gen-ph]

Sylvain Joubaud, Artem Petrosyan, Sergio Ciliberto, Nicolas B. Garnier. Experimental evidence of non-Gaussian fluctuations near a critical point.. 2008. ⟨ensl-00255014v1⟩