Diagrammatic approach proposed many years ago for strong correlated Hubbard
model is developed for analyzing of the thermodynamic potential properties. The
new exact relation between such renormalized quantities as thermodynamic
potential, one-particle propagator and correlation function is established.
This relation contains additional integration of the one-particle propagator by
the auxiliary constant. The vacuum skeleton diagrams constructed from
irreducible Green's functions and tunneling propagator lines are determined and
special functional is introduced. The properties of such functional are
investigated and its relation to the thermodynamic potential is established.
The stationary properties of this functional with respect to first order
changing of the correlation function is demonstrated and as a consequence the
stationary properties of the thermodynamic potential is proved.Comment: 6 pages, 4 figure
