Fluctuations of the hydrodynamic fields in a driven granular fluid induce effective long-range forces between the immersed intruder particles. By means of numerical simulations and analytical calculations we verify that the Casimir-like force between two immobile intruders is attractive when the volume fraction of the granular fluid is sufficiently high. However, a crossover from attraction to repulsion occurs as the density decreases. The distance between the intruders, and the restitution coefficient are the other control parameters of the transition. We investigate the nonadditive property of the interactions, and clarify the impact of dimensionality and particle shape.

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