Max-Planck-Institut für Festkörperforschung, Stuttgart;
Department of Physics, University of Illinois, Urbana, Illinois 6180

A discrete Hubbard-Stratonovich transformation is presented for systems with an orbital degeneracy N and a Hubbard Coulomb interaction. An exact transformation is obtained by introducing an external field which takes N+1 values. Alternative approximate transformations are presented, where the field takes fewer values, for instance two values corresponding to an Ising spin.

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Physics Letters A, 235 530-4, 1997.