In this talk I will discuss binary black hole mergers in cubic Horndeski theories of gravity, which are known to have a well-posed initial value problem in the standard CCZ4 formulation of the Einstein equations. In our work we consider black hole binary mergers in this class of theories treating Horndeski terms fully non-linearly whilst ensuring that the theory remains in the regime of validity of EFT. As we shall see, even if the Horndeski terms are suitably small at all times, over long enough times (e.g., a few orbits of the binary), small effects accumulate giving rise to significant differences compared to standard GR. Time permitting, towards the end of the talk I will discuss how one can study black hole binaries in higher derivative theories of gravity.
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