Zenithal gliding of the easy axis of a nematic liquid crystal.

We present experimental evidence of zenithal gliding of the nematic easy axis on a polyimide surface. The reorientation dynamics of the easy axis under external torque, and its relaxation, are extremely slow processes which cannot be described by a single exponential time. They show similarities with aging phenomena previously encountered in glassy systems. At last, the adsorption-desorption-readsorption process which empirically justifies the azimuthal easy axis gliding may also explain our observations.