On Newton-Cartan trace anomalies

We classify the trace anomaly for parity-invariant non-relativistic Schr\"odinger theories in 2+1 dimensions coupled to background Newton-Cartan gravity. The general anomaly structure looks very different from the one in the z=2 Lifshitz theories. The type A content of the anomaly is remarkably identical to that of the relativistic 3+1 dimensional case, suggesting the conjecture that an a-theorem should exist also in the Newton-Cartan context. Erratum: due to an overcounting of the number of linearly-independent terms in the basis, the type A anomaly disappears if Frobenius condition is imposed. See appended erratum for details. This crucial mistake was pointed out to us in arXiv:1601.06795.