Continuum mesoscale theory inspired by plasticity
  We present a simple mesoscale field theory inspired by rate-independent plasticity that reflects the symmetry of the deformation process. We parameterize the plastic deformation by a scalar field which evolves with loading. The evolution equation for that field has the form of a Hamilton-Jacobi equation which gives rise to cusp-singularity formation. These cusps introduce irreversibilities analogous to those seen in plastic deformation of real materials: we observe a yield stress, work hardening, reversibility under unloading, and cell boundary formation. 
J.P. Sethna (Cornell), M. Rauscher (Max-Planck-Institute, Stuttgart),   J.-P. Bouchaud (CEA-Saclay)