Finite size effects and ageing near a critical point

Abstract

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 distribution. The latter is recovered away from the critical point. We also show that after a quench at the critical point the system presents ageing properties.

Keywords:

• non-Gaussian statistics
• Gumbel
• ageing
• critical point
• fluctuations dissipations relations
• finite size
• ellipsometry
• soft matter
• statistical physics

Acknowledgements

We acknowledge useful discussion with R. Benzi, P. Holdsworth and J.F. Pinton. This work has been partially supported by ANR-05-BLAN-0105-01.