Peculiarities of oscillator with nonlinear cordinate-dependent mass

A nonlinear model of the scalar field with a coupling between the field and its gradient is developed. It is shown, that such model is suitable for the description of phase transition accompanied by formation of spatial inhomogeneous distribution of the order parameter. The proposed model is analogous the mechanical nonlinear oscillator with the coordinate-dependent mass or velocity-dependent elastic module. Besides, for some value of energy the model under consideration possesses exact analytical solution. We assume that this model can related to the spinodal decomposition, quark confinement, or cosmological scenario. All predictions can be verified experimentally.