Instanton method for the electron propagator

A nonperturbative theory of the electron propagator is developed and used to calculate the one-particle Green's function and tunneling density-of-states in strongly correlated electron systems. The method, which is based on a Hubbard-Stratonovich decoupling of the electron-electron interaction combined with a cumulant expansion of the resulting noninteracting propagator, provides a possible generalization of the instanton technique to the calculation of the electron propagator in a many-body system. Application to the one-dimensional electron gas with short-range interaction is discussed.