Emergent gravity in superplastic crystals and cosmological constant problem

We discuss emergent gravity in the superplastic crystals. We restrict ourselves by the consideration of the gapped (massive) fermions coupled to gravity. In this approach the stress - energy tensor may be defined in such a way, that being integrated over the whole volume it is a topological invariant provided that the background metric weakly depends on coordinates. In equilibrium its value is not changed if the system is modified smoothly. The cosmological constant in this pattern is a topological invariant as well.