Classical and tree-level approaches to gravitational deflection in higher-derivative gravity

TL;DR

This paper investigates photon gravitational deflection in higher-derivative gravity, providing new bounds on theory parameters by analyzing classical and semiclassical light bending near the Sun, thus advancing tests of quantum gravity models.

Contribution

It introduces a novel analysis of photon deflection in higher-derivative gravity and establishes tighter bounds on the theory's parameters based on classical and semiclassical calculations.

Findings

Derived an upper bound on the R^2_{ u e9} sector constant.

Improved existing constraints on higher-derivative gravity parameters.

Confirmed the consistency of higher-derivative gravity with observed light bending.

Abstract

Among the so-called classical tests of general relativity (GR), light bending has been confirmed with an accuracy that increases as times goes by. Here we study the gravitational deflection of photons within the framework of classical and semiclassical higher-derivative gravity (HDG) -- the only version of GR that is known up to now to be renormalizable along with its matter couplings. Since our computations are restricted to scales much below the Planck cut-off we need not be afraid of the massive spin-2 ghost that haunts HDG. An upper bound on the constant related to the $R^2_{\mu \nu}$-sector of the theory is then found by analyzing -- from a classical and semiclassical viewpoint -- the deflection angle of a photon passing by the Sun. This upper limit greatly improves that available in the literature.