ABSTRACT
Our general procedure for describing transport phenomena will be based on approximations in which g 2(U), which appears in the equation of motion for g(U), is expanded in terms of g(U). The simplest approximation of this nature is the Hartree approximation. g 2 12 ; 1 ′ 2 ′ ; U = g 1 , 1 ′ ; U g 2 , 2 ′ ; U $$ g_{2} \left( {12;1'2';U} \right) = g\left( {1,1';U} \right)g\left. {\left( {2,2';} \right)U} \right) $$ https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315196596/a397f31e-8107-49bb-8694-b978d38168d6/content/math8_1.tif"/>
