Causality constraints in Quadratic Gravity

A bstract Classifying consistent effective field theories for the gravitational interaction has recently been subject of intense research. Demanding absence causality violation in high energy graviton scattering processes led to a hierarchy constraints on higher derivative terms Lagrangian. Most these have relied analysis that is performed general relativistic backgrounds, as opposed generic solution equations motion which are perturbed by curvature operators. Hence, necessary but may not be sufficient ensure theory consistent. In this context, we explore so-called CEMZ Quadratic Gravity space shock wave solutions beyond GR. We show Shapiro time delay experienced polarization-independent and positive, regardless strength couplings. Our shows far concerned, albeit inequivalent General Relativity due additional propagating modes, causal per diagnostic proposed CEMZ.