Sticky grains do not change the universality class of isotropic snadpiles

Juan A. Bonachela1, José J. Ramasco2, Hugues Chaté3, Ivan Dornic3 and Miguel A. Muñoz1
1 Instituto de Física Teórica y Computacional Carlos I, Facultad de Ciencias, Univ. de Granada, 18071 Granada, Spain.
2Physics Department, Emory University, Atlanta GA 30322, USA.
3CEA, Service de Physique de l'État Condensé, CEN Saclay, 91191 Gif-sur-Yvette, France.

(June 2006)

We revisit the sandpile model with "sticky" grains introduced by Mohanty and Dhar [Phys. Rev. Lett. 89, 104303 (2002)] whose scaling properties were claimed to be generically in the universality class of directed percolation for both isotropic and directed models. While for directed models this conclusion is unquestionable, for isotropic models we present strong evidence that the asymptotic scaling in the self-organized regime in which a stationary critical state exists in the limit of slow driving and vanishing dissipation rate is, like other stochastic sandpiles, generically in the Manna universality class. This conclusion is drawn from extensive Monte Carlo simulations, and is strengthened by the analysis of the Langevin equations proposed by the same authors to account for this problem , argued to converge upon coarse-graining to the well-established set of Langevin equations for the Manna class.