title: Force correlations in the q model for general q distributions.
abstract: We study force correlations in the q model for granular media at infinite depth for general q distributions. We show that there are no two-point force correlations as long as q values at different sites are uncorrelated. However, higher-order correlations can persist, and if they do, they only decay with a power of the distance. Furthermore, we find the entire set of q distributions for which the force distribution factorizes. It includes distributions ranging from infinitely sharp to almost critical. Finally, we show that two-point force correlations do appear whenever there are correlations between q values at different sites in a layer; various cases are evaluated explicitly.
authors.affiliation: Instituut-Lorentz, Leiden University, P.O. Box 9506, 2300 RA Leiden, The Netherlands.
authors.forename: Jacco H
authors.initials: JH
authors.lastname: Snoeijer
authors.forename: J M J
authors.initials: JM
authors.lastname: van Leeuwen