Dynamics of a liquid crystal close to the Fréedericksz transition
We study experimentally and numerically the dynamics of the director of a liquid crystal driven by an electric field close to the critical point of the Fréedericksz transition (FT). We show that the Landau-Ginzburg (LG) equation, although it describes correctly the stationary features of FT in a rather large range of the control parameter, cannot be used to describe the dynamics in the same range. The reasons of this discrepancy are related not only to the approximations done to obtain this equation but most importantly to the finite value of the anchoring energy and to small asymmetries on boundary conditions. The difference between static and dynamics is discussed. These results are useful in all of the cases where FT is used as an example for other orientational transitions.