Integrable non-linear sigma models with fermions

The two-dimensional non-linear sigma model on a Riemannian symmetric space M=G/H is coupled to fermions with quartic self-interactions. The resulting hybrid model is presented in a gauge-dependent formulation, with a bosonic field taking values in G and a fermionic field transforming under a given representation of the gauge group H. General criteria for classical integrability are presented: they essentially fix the Lagrangian of the model but leave the fermion representation completely arbitrary. It is shown that by a special choice for the fermion representation (derived from the adjoint representation of G by an appropriate reduction) one arrives naturally at the supersymmetric non-linear sigma model on M=G/H. The issue of quantum integrability is also discussed, though with less stringent results. (orig.)