Key points are not available for this paper at this time.
Characteristic classes for the index of the Dirac family unk(A) are computed in terms of differential forms on the orbit space of vector potentials under gauge transformations. They represent obstructions to the existence of a covariant Dirac propagator. The first obstruction is related to a chiral anomaly.
Atiyah et al. (Sun,) studied this question.
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