LINEAR RESPONSE THEORY: A HISTORICAL PERSPECTIVE

Abstract

A survey is given of the development of the linear response theory of transport processes in Japan in a short period between early 1955 and late 1956, immediately after the discovery of the formula for electrical conductivity. Although the article gives a historical account, it also provides sufficient pedagogical material for those who wish to study linear response theory. The conventional theory based on the Boltzmann-Bloch equation is also briefly reviewed for the sake of pedagogical completeness. To clarify the origin of irreversibility, variational principles of transport processes are described including Onsager’s thermostatistical theory, which are well known in conjunction with the reciprocity relations of transport coefficients. These variational principles correspond to various levels of the description of nonequilibrium systems. Contraction of microscopic to a macroscopic information transforms one variational principle into another. A reflection upon the foundation of linear response theory is given through the comparison of two different traditional theories of transport processes, Thomson’s theory of thermoelectricity and Onsager’s thermostatistical theory.