Anomalous Transport Due to the Conformal Anomaly

TL;DR

This paper demonstrates how the conformal anomaly in field theories induces novel anomalous transport phenomena, such as electric currents, in external electromagnetic and gravitational backgrounds, revealing new effects linked to the beta function.

Contribution

It introduces the scale electric and magnetic effects, showing how conformal anomalies generate dissipationless currents in inhomogeneous gravitational fields.

Findings

Electric current flows opposite to background electric field in inflating geometry.

Transverse electric currents occur in static inhomogeneous gravitational backgrounds.

Currents are proportional to the beta function of the theory.

Abstract

We show that the scale (conformal) anomaly in field theories leads to new anomalous transport effects that emerge in an external electromagnetic field in an inhomogeneous gravitational background. In inflating geometry the QED scale anomaly locally generates an electric current that flows in opposite direction with respect to background electric field (the scale electric effect). In a static spatially inhomogeneous gravitational background the dissipationless electric current flows transversely both to the magnetic field axis and to the gradient of the inhomogeneity (the scale magnetic effect). The anomalous currents are proportional to the beta function of the theory.