Rigorous results in the theory of superconductivity with Coulomb-like repulsion

The traditional method of the approximating hamiltonian is applied for the investigation of a model of a superconductor with interaction of the BCS type and Coulomb-like repulsion, the latter being described by unbounded operators. It is shown that the traditional method can be generalized in such a way that for the model under consideration one can prove the asymptotic (in the thermodynamic limit V → ∞) coincidence not only of the free energies (per unit volume) but also of the correlation functions of the model and approximating hamiltonians.