Description of the phase with broken symmetry in the Ising model by the method of quasi-averages

A system of equations for the correlation functions of the Ising model is obtained. It is shown that this system of equations is solvable at a sufficiently low temperature and a rapidly converging iterative procedure is constructed which makes it possible to calculate with arbitrarily high accuracy the equation of state and the correlation functions of the Ising model. The first terms of the perturbation theory series are given.