Principle of stationary action in the theory of superfluid systems with spontaneously broken translational symmetry

摘要

We construct a Lagrangian describing the low-frequency dynamics of a system with spontaneously broken phase and translational symmetry (a supersolid). Using the principle of stationary action, we obtain the hydrodynamic equations for the considered system. We give a relativistic generalization of the obtained equations of motion in terms of the the Gibbs thermodynamic potential density.