FUNCTIONAL INTEGRAL APPROACH TO THE SINGLE IMPURITY ANDERSON MODEL

Recently, a functional integral representation was proposed by Weller [1), in which the fermionic fields strictly satisfy the constraint of no double occupancy at each lattice site. This is achieved by introduc ing spin dependent Bose fields. The functional integral method is appl ied to the single impurity Anderson model both in the Kondo and mixed- valence regime. The f-electron Green's function and susceptibility are calculated using an Ising-like representation for the Bose fields. We discuss the difficulty to extract a spectral function from the knowle dge of the imaginary time Green's function. The results are compared w ith NCA calculations.