Properties of layer-by-layer vector stochastic models of force fluctuations in granular materials

We attempt to describe the stress distributions of granular packings using lattice-based layer-by-layer stochastic models that satisfy the constraints of force and torque balance and nontensile forces at each site. The inhere nt asymmetry in the layer-by-layer approach appears to lead to an asymmetri c force distribution, in disagreement with both experiments and general sym metry considerations. The vertical force component probability distribution is robust and in agreement with predictions of the: scalar q model of Lm e t at. [Science 269, 513 (1995)] and Coppersmith ed at. [Phys. Rev. E 53, 46 73 (1996)]while the distribution of horizontal force components is qualitat ively different and depends on the details of implementation. [S1063-651X(9 9)13505-0].