On the problem of high temperature superconductivity

This article is a brief review of the present situation in theoretical investigations of high temperature superconductivity. The main subject is a discussion of the formula for a critical temperature T_c for a homogeneous and isotropic substance with arbitrary permeability ?(q, ω). The problem of the maximum possible value of T_c is discussed. It is concluded that at present there are no grounds to consider that values of T_c ? 100°K to be impossible. The paper ends with some remarks on the exciton mechanism of superconductivity for the case of superconductors with a plane geometry.