ABSTRACT
This theorem re la tes the correlation function to the
imaginary part of the response function:
C(k, ud) = - Im G(k, ou) (14.12) 0)
It can be tr iv ia lly satisfied to zeroth order, as (14.6) shows,
and easily proven in a m icroscop ic theory. Also, in a
formal way, it can be shown to follow from our general
kinetic equations. Here let us illustrate how this theorem
may be satisfied by studying graphs. The reader can gain
some insight into the structure of graphs through this
illustration.
