We consider the introduction of fluctuation corrections to saddle-point results in the symmetric treatment of a mixed pseudofermion-boson representation of correlated electrons. In our calculations we avoid the complications of working in the discrete imaginary-time formulation of the functional integral, a procedure recently advocated in the literature as mandatory for this problem. For a simple two-site model our approach leads to approximate results in remarkable agreement with the exact results, and without the spurious nonanalyticities of other similar treatments.

• Received 11 July 1995

DOI:https://doi.org/10.1103/PhysRevB.52.14511