Experimental limits on the free parameters of higher-derivative gravity

TL;DR

This paper reviews experimental constraints on the free parameters of higher-derivative gravity, focusing on limits derived from relativistic and laboratory tests, with the tightest bounds coming from light deflection measurements.

Contribution

It provides a comprehensive review of experimental limits on the parameters of higher-derivative gravity, highlighting the most stringent bounds from light deflection.

Findings

Relativistic and laboratory experiments set upper limits on the parameters.

The tightest limit on $eta$ comes from semiclassical light deflection.

Bounds on $eta$ are only an order of magnitude larger than those from other tests.

Abstract

Fourth-derivative gravity has two free parameters, $\alpha$ and $\beta$, which couple the curvature-squared terms $R^2$ and $R_{\mu\nu}^2$. Relativistic effects and short-range laboratory experiments can be used to provide upper limits to these constants. In this work we briefly review both types of experimental results in the context of higher-derivative gravity. The strictest limit follows from the second kind of test. Interestingly enough, the bound on $\beta$ due to semiclassical light deflection at the solar limb is only one order of magnitude larger.