- #1

DrDu

Science Advisor

- 6,044

- 763

While I can follow the steps of the calculation, the physical content is not quite clear to me.

While the difference between a free and a "dressed" Greens function is quite clear to me, the

concept of a dressed vertex is much less. I only see it as a formal device to calculate the current-current correlation functions. The collective modes somehow fall out as homogeneous solutions of a Bethe Salpeter type equation.

Schrieffer stresses that the mechanism in fact is not peculiar to superconductivity but holds also in normal metals. I know of some discussions of the "backflow" which is also not too clear to me. I suppose that these matters are better understood now half a century later. Maybe someone knows a more pedagogical reference?