Subharmonic Instabilities and Defects in a Granular Layer under Vertical Vibrations

摘要: We report an experimental study of subharmonic instabilities observed in a horizontal layer glass spheres under vertical vibrations. Above critical value the acceleration, undergoes period-doubling instability. When acceleration is increased further, spatially homogeneous temporal oscillation at half excitation frequency becomes unstable and regular pattern defects generated. Each defect separates two regions oscillating out phase, thus connected with discrete broken symmetry bifurcation.