Cracking stones and throwing sand are my favorite but I do that peacefully either on the computer or a sheet of paper.

Presently I am working also on dunes and Apollonian packings.

I have also investigated density  waves, fragmentation, stratification, segregation, compactification, sedimentation, dissipative gases, the shape of a sand pile, the dip under the heap, non-linear elasticity of packings and shear bands which I also studied micromechanically.

Among others I have been working with Lucilla de Arcangelis on SOC on small world lattices and the brain, with Falk Wittel and Norbert Stoop on folding of wire, with Ferenc Kun and Raul Cruz on fibres, with Jose Soares on complex networks and on porous media and with Jason Gallas on cellular automata.

In the past I have worked on percolation, kinetic gelation, cluster-cluster aggregation, traffic, mineral dendrites, superplasticity and the Potts model and have written reviews on cellular automata, fracture, growth phenomena and geometrical critical phenomena.

Also I am managing editor of
International J. of Modern Physics C and of
Granular Matter , in the editorial board of several journals
and have edited several books .