RESTRICTED PATH-INTEGRAL APPROACH TO THE DOPED HUBBARD-MODEL

We present a restricted path integral approach to the 2D repulsive Hub bard model. It amounts to evaluating the partition function by restric ting the summation over states to a small subclass and generalizes mea n-field theory. Analyzing the simplest of these approximations, we fin d a mixed phase of fermions with local antiferromagnetic correlations coexisting with conventional metallic fermions. This mixed phase persi sts in a big parameter regime. We also discuss a refinement of our app roximation which suggests simple explanations of several peculiar expe rimental features of HTSC.