Determination of Angle of Light Deflection in Higher-Derivative Gravity Theories

TL;DR

This paper introduces iterative methods to compute the gravitational light deflection angle in advanced gravity theories where explicit solutions are difficult, revealing that deflection angles are always below Einstein's classical value and decrease with photon energy.

Contribution

It develops globally convergent iterative techniques for calculating deflection angles in higher-derivative gravity theories, establishing universal properties of the deflection angle behavior.

Findings

Deflection angle always below Einstein angle

Deflection angle decreases with photon energy

Iterative methods effectively compute deflection in complex theories

Abstract

Gravitational light deflection is known as one of three classical tests of general relativity and the angle of deflection may be computed explicitly using approximate or exact solutions describing the gravitational force generated from a point mass. In various generalized gravity theories, however, such explicit determination is often impossible due to the difficulty with obtaining an exact expression for the deflection angle. In this work, we present some highly effective globally convergent iterative methods to determine the angle of semiclassical gravitational deflection in higher- and infinite-derivative formalisms of quantum gravity theories. We also establish the universal properties that the deflection angle always stays below the classical Einstein angle and is a strictly decreasing function of the incident photon energy, in these formalisms.