THE CUMULANT APPROXIMATION FOR FEYNMAN PROPAGATORS

The following sections are included:

• Introduction

• The Cumulant Approximation

• Spectrum of Positionally Disordered Systems

  • Basic formulation

  • Evaluation of G

  • The behaviour of density of states

  • The density of states for Gaussian correlation

• The Polaron Problem

  • Free energy and ground state energy

  • The effective mass

• The Bi-Polaron Problem

• Polymer Distribution Functions

• Notes and References