QED trace anomaly, non-local Lagrangians and quantum Equivalence Principle violations

TL;DR

This paper derives the trace anomaly using a non-local effective action, highlighting infrared physics, and demonstrates that quantum effects can cause violations of the classical equivalence principle, such as frequency-dependent light bending.

Contribution

It introduces a simple form of the trace anomaly via a non-local effective action and explores its implications for quantum violations of the equivalence principle.

Findings

Long-distance quantum corrections lead to violations of classical equivalence principle predictions.

The non-local effective action explicitly displays the full energy-momentum tensor.

Quantum effects induce frequency dependence in gravitational light bending.

Abstract

We discuss the derivation of the trace anomaly using a non-local effective action at one loop. This provides a simple and instructive form and emphasizes infrared physics. We then use this example to explore several of the properties of non-local actions, including displaying the action for the full non-local energy-momentum tensor. As an application, we show that the long-distance corrections at one loop lead to quantum violations of some classical consequences of the equivalence principle, for example producing a frequency dependence of the gravitational bending of light.