HEP Theory Journal Club

Causality and modifications to Einstein's gravity

Simon Caron-Huot

McGill

Does our world respect causality at all energy scales? We explore constraints on gravitational dynamics which stem from this assumption. Parameterizing long-distance effects of possible new heavy particles using effective field theory (EFT), we study causality of 2 to 2 scattering processes. Due to its energy growth, the gravitational force turns out to be particularly difficult to modify. I will present two-sided bounds which show that a wide class of modifications to four-dimensional Einstein's gravity require the existence of light higher-spin states, and speculate on their possible couplings to the Standard Model.