Bending of Light in Quantum Gravity

TL;DR

This paper calculates quantum corrections to light bending near massive objects using effective field theory, revealing potential violations of classical equivalence principles.

Contribution

It provides the first direct computation of quantum gravitational effects on light bending, including long-range quantum contributions.

Findings

Quantum corrections modify classical light bending angles.

Long-range quantum effects can violate classical equivalence principles.

Results are applicable to light scattering by massive astrophysical objects.

Abstract

We consider the scattering of lightlike matter in the presence of a heavy scalar object (such as the Sun or a Schwarzschild black hole). By treating general relativity as an effective field theory we directly compute the nonanalytic components of the one-loop gravitational amplitude for the scattering of massless scalars or photons from an external massive scalar field. These results allow a semiclassical computation of the bending angle for light rays grazing the Sun, including long-range $\hbar$ contributions. We discuss implications of this computation, in particular the violation of some classical formulations of the equivalence principle.