The two-loop β-function for σ-models with torsion

We compute, at the two-loop order of perturbation theory, the β-functions governing the renormalization of the target space metric tensor gij and torsion potential bij of the general bosonic two-dimensional nonlinear σ-model. We pay particular attention to problems with alternating tensors in dimensional regularization. Our results, which have a consistent string theory interpretation, disagree with those published previously by other authors. (orig.)