Olle Gunnarsson (a) and Erik Koch (b)
(a) Max-Planck-Institut fuer Festkoerperforschung, Stuttgart
(b) Department of Physics, University of Illinois, Urbana-Champaign
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.
Phys. Lett. A 235, R530 (1997).
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