Mass of quasi-particles

Spontaneous symmetry breaking in the system “dielectric medium- electromagnetic field” is considered. The appearance of massive quasi-particles in a boundless dielectric medium, a dielectric resonator and a dielectric waveguide is shown. The mass of the quasi-particles arises because they move in the medium or the waveguide with the velocity less than the speed of light in vacuum, as a result of interaction of electromagnetic field and the medium.