We investigate time delays of wave scatterings around black hole backgrounds in scalar-tensor effective field theories of gravity. The scalar-Gauss-Bonnet (sGB) couplings, being corrections of the lowest orders, can give rise to hairy black holes. By requiring infrared causality, we impose lower bounds on the cutoff scales of the theories. With these bounds, we further discuss the detectability of sGB gravity in gravitational waves from binary black hole mergers. Compared with the gravitational effective field theories that contain only the two tensor modes, adding extra degrees of freedom, such as adding a scalar, opens up a detectable window in the planned observations.
@article{arxiv.2410.10973,
title = {Scalar-Gauss-Bonnet gravity: Infrared causality and detectability of GW observations},
author = {Wen-Kai Nie and Lin-Tao Tan and Jun Zhang and Shuang-Yong Zhou},
journal= {arXiv preprint arXiv:2410.10973},
year = {2025}
}