What is an anomaly?
arXiv:2307.08147
Abstract
The anomaly of a quantum field theory is an expression of its projective nature. This starting point quickly leads to its manifestation as a special kind of field theory: a once-categorified invertible theory. We arrive at this statement through a general discussion of projectivity and a discussion of projectivity in quantum mechanics. We conclude with a general formula for the anomaly of a free spinor field.
20 pages, 3 figures