2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/16701An ensemble of inelastically colliding grains driven by a vibrating wall in 2D exhibits density clustering. Working in the limit of nearly elastic collisions and employing granular hydrodynamics, we predict, by a marginal stability analysis, a spontaneous symmetry breaking of the extended clustering state (ECS). 2D steady-state solutions found numerically describe localized clustering state (LCSs). Time-dependent granular hydrodynamic simulations show that LCSs can develop from natural initial conditions. The predicted instability should be observable in experiment.4 pages, 4 eps figuresSoft Condensed MatterPattern Formation and SolitonsFluid Dynamicstext