Faraday Waves on a Viscoelastic Liquid

We investigate Faraday waves on a viscoelastic liquid. Onset measurements and a nonlinear phase diagram for the selected patterns are presented. By virtue of the elasticity of the material a surface resonance synchronous to the external drive preempts the usual subharmonic Faraday instability. Close to the bicriticality, the nonlinear wave interaction gives rise to a variety of novel surface states: sharply localized islands of hexagons or superlattices and hexagons or superlattices coexisting with line patterns of a different spatial periodicity length. Theoretical stability calculations on the basis of the rheometric viscosity data and qualitative resonance arguments support the experimental observations.