Many-body coherent potential approximation, dynamical coherent potential approximation, and dynamical mean-field theory

The coherent potential approximation (CPA) is a useful tool to describe the electron correlations as well as the effects of disorder on electrons. Among various theories of correlated electron systems, the many-body CPA, the dynamical CPA, and the dynamical mean-field theory have been investigated in great detail from the viewpoint of the CPA. It is demonstrated that these three theories are equivalent to each other, so that the theories of itinerant magnetism and those of the strongly correlated electron systems are unified within the single-site approximation. This explains why the Neel temperatures calculated by the dynamical mean-field theory agree well with the ones calculated by the classical and adiabatic versions of the dynamical CPA, the single-site spin-fluctuation theory, and the variational approach.