  In the paper, the inhomogeneous states with local translational symmetry are
under investigation in the framework of the Landau theory. The phonon potential
is defined as a compensating field of local representation of the subgroup of
translations. The constructed phenomenological Ginzburg-Landau potential takes
into account both electromagnetic and electron-phonon interactions explicitly.
The suggested phenomenological model does not require doubling of charge to get
the correct expression of current density in the Londons equations and is in
agreement with the BCS model. A phenomenological description of sound based on
the phonon potential is also proposed.
