Anomalies,ambiguities and superstrings

It is shown that anomalies only change trivially if a covariant term is added to the gauge connection. As a result, for the superstring, the anomalies can be cancelled if the anti-symmetric tensor field strength H is modified by the Chern-Simons form of any spin-connection, possibly with torsion. The low-energy effective field theory is, then, not uniquely determined by requiring anomaly cancellation and supersymmetry. Implications for string compactifications are considered.