Microscopic derivation of nonlinear fluctuating hydrodynamics for crystalline solid

We present a microscopic derivation of the nonlinear fluctuating hydrodynamic equation for the homogeneous crystalline solid from the Hamiltonian description of a many-particle system. We propose a microscopic expression of the displacement field that correctly generates the nonlinear elastic properties of the solid and find the nonlinear mode-coupling terms in reversible currents which are consistent with the phenomenological equation. The derivation relies on the projection onto the coarse-grained fields including the displacement field, the long-wavelength expansion, and the stationarity condition of the Fokker-Planck equation.