The spectrum of gauge theories in the frame of many-body approximations

In a recent paper, the author has proposed to apply non-perturbative many-body techniques to the eigenvalue problem of gauge field theories. Similar to other approaches in this direction the aim hereby is to gain insights into the structure of these theories which represent alternatives to lattice calculations. It is the purpose of this talk to describe the basic principles of our approach (our treatment of renormalization, the general structure of the gauge field-theoretical Hamiltonian and the cluster expansion techniques proposed to approximate its eigenvlalue problem) and some first results. (orig.)