  We consider the problem important for the condensed matter physics,
superconductivity physics, and electrodynamics of continuous media - the
problem of the matter dielectric permittivity possible values spectrum
definition. Two ways of the dielectric permittivity values spectrum
identification are analyzed. The proposed technique allows the author to
complete the universal criterion of stability identified by D. A. Kirzhnits for
a system of charged particles by the criterion of stability for a
superconducting system of charged particles.
