  Motivated by the large strain shear of loose granular materials we introduced
a model which consists of consecutive optimization and restructuring steps
leading to a self organization of a density field. The extensive connections to
other models of statistical phyics are discussed. We investigate our model on a
hierarchical lattice which allows an exact asymptotic renormalization
treatment. A surprisingly close analogy is observed between the simulation
results on the regular and the hierarchical lattices. The dynamics is
characterized by the breakdown of ergodicity, by unusual system size effects in
the development of the average density as well as by the age distribution, the
latter showing multifractal properties.
