Fundamental length scale and the bending of light in a gravitational field

TL;DR

This paper explores how a minimal length scale, suggested by quantum gravity theories, affects light bending in a gravitational field, proposing a potentially measurable quantum gravity effect.

Contribution

It combines modified dispersion relations from Double Special Relativity with effective field theory to compute post-Newtonian light bending corrections.

Findings

First post-Newtonian correction to light bending calculated

Potential measurable effect linked to quantum gravity and minimal length

Supports experimental tests for quantum spacetime theories

Abstract

The canonical approach to quantizing quantum gravity is understood to suffer from pathological non-renomalizability. Nevertheless in the context of effective field theory, a viable perturbative approach to calculating elementary processes is possible. Some non-perturbative approaches, most notably loop quantum gravity and combinatorial quantum gravity imply the existence of a minimal length. To circumvent the seeming contradiction between the existence of a minimum length and the principle of special relativity, Double Special Relativity introduces modified dispersion relationships that reconcile the conflict. In this work, we combine these dispersion relationships with an effective field theory approach to compute the first post Newtonian correction to the bending of light by a massive object. The calculation offers the prospect of a directly measurable effect that rests upon both the existence of a quantized gravitational field and a minimal length. Experimental verification would provide evidence of the existence of a quantum theory of gravity, and the fundamental quantization of spacetime with a bound on the minimal distance.