Experimental limits on the free parameters of higher-derivative gravity

Fourth-derivative gravity has two free parameters, α and β, which couple the curvature-squared terms R² 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 β due to semiclassical light deflection at the solar limb is only one order of magnitude larger.