Trace anomalies and the string-inspired definition of quantum-mechanical path integrals in curved space

TL;DR

This paper compares string-inspired and quantum field theory approaches to quantum-mechanical path integrals in curved space, revealing that the string-inspired method yields incorrect local trace anomalies due to coordinate invariance issues.

Contribution

It demonstrates that the string-inspired path integral method produces incorrect local trace anomalies and clarifies the role of coordinate invariance in both approaches.

Findings

String-inspired method gives incorrect local trace anomalies.

Quantum field theory approach yields correct anomalies.

Both methods agree on integrated trace anomalies.

Abstract

We consider quantum-mechanical path integrals for non-linear sigma models on a circle defined by the string-inspired method of Strassler, where one considers periodic quantum fluctuations about a center-of-mass coordinate. In this approach one finds incorrect answers for the local trace anomalies of the corresponding $n$-dimensional field theories in curved space. The quantum field theory approach to the quantum-mechanical path-integral, where quantum fluctuations are not periodic but vanish at the endpoints, yields the correct answers. We explain these results by a detailed analysis of general coordinate invariance in both methods. Both approaches can be derived from the same operator expression and the integrated trace anomalies in both schemes agree. In the string-inspired method the integrands are not invariant under general coordinate transformations and one is therefore not permitted to use Riemann normal coordinates.