Memory Functions, Projection Operators, and the Defect Technique: Some Tools of the Trade for the Condensed Matter Physicist

Subir Sachdev A

Alexei M. Tsvelik

V. M. Kenkre

Jaime Merino, A. Levy Yeyati

Nabyendu Das, Pankaj Bhalla, Navinder Singh

Memory function formalism or projection operator technique is an extremely useful method to study the transport and optical properties of various condensed matter systems. A recent revival of its uses in various correlated electronic systems is being observed. It is being used and discussed in various contexts, ranging from nonequilibrium dynamics to the optical properties of various strongly correlated systems such as high temperature superconductors. However, a detailed discussion on this method, starting from its origin to its present day applications at one place is lacking. In this paper, we attempt a comprehensive review of the memory function approach focusing on its uses in studying the dynamics and the transport properties of correlated electronic systems.

Leo P. Kadanoff, Gordon Baym

This book is a very early systematic treatment of the application of the field-theoretical methods developed after the Second World War to the quantum mechanical many-body problem at finite temperature. It describes various techniques that remain basic tools of modern condensed matter physicists.