Periodic spatial forcing can strongly influence selection of stationary patterns near a symmetry-breaking bifurcation point. The following effects are demonstrated by use of simple model equations of long-scale thermal convection: (a) transition between alternative patterns; (b) emergence of spatially quasiperiodic patterns; and (c) evolution of patterns due to rotating phases.

• Received 30 March 1987

DOI:https://doi.org/10.1103/PhysRevLett.59.2740