Causality violation in a weakly coupled theory of gravity

Causality Constraints on Corrections to the Graviton Three-Point Coupling

We consider higher derivative corrections to the graviton three-pointcoupling within a weakly coupled theory of gravity.We argue that these are constrained by causality.We devise a thought experiment involving a high energy scattering process which leads to causality violation if the graviton three-point vertex contains the additional structures.This violation can be fixed by adding an infinite tower of extra massive particles with higherspins.This implies a constraint on the conformal anomaly coefficients in terms of the dimension of the lightest single particle operator with spin.