I have measured the penetration length $\xi$ of a vortex into a subcritical region, using the electroconvective instability in a liquid crystal. $\xi$ corresponds to the correlation length of the order-parameter fluctuations in a second-order phase transition and is found to have a mean-field behavior. Moreover, I have found a new effect: propagation of solitary vortices over a distance equal to that correlation length.

• Received 3 January 1979

DOI:https://doi.org/10.1103/PhysRevLett.42.1212