Periodic, aperiodic, and transient patterns in vibrated granular layers

Experiments on vertically vibrated granular layers in evacuated containers reveal a variety of patterns for acceleration amplitudes above a critical value (≈2.5g). Stripes, squares, hexagons, spirals, triangles, and targets, as well as particle-like localized excitations (“oscillons”) and fronts (“kinks”) between regions with different vibrational phase are observed as the layer depth and the container oscillation frequency and amplitude are varied. A zig-zag instability, unstable hexagons, phase-disordered patterns, and “two-phase” squares are also observed. With a few noteworthy exceptions, the patterns are essentially independent of the lateral boundary conditions.