Ward Identity as Exact Transport Equation

Abstract

We show that the exact transport equation of interacting fermions is nothing but an alternative form of the Ward identity. It is close to that derived diagrammatically by ´ Eliashberg, but along with the complete collision integral and full renormalizations. We further discuss the hidden divergence in conductivity in the conventional microscopic Fermi liquid theory. The exact transport equation does not bring this divergence, incorporating the particleparticle and hole-hole excitations. Subject Index: 052, 062, 323, 356