Black Holes as Probes of an Effective Field Theory Extension to General Relativity

Direct observation of gravitational waves (GW) from merging black holes has opened up the possibility of exploring the theory of gravity in the strong regime at an unprecedented level. It is therefore interesting to explore which extensions to General Relativity (GR) could be detected. An Effective Field Theory (EFT) satisfying the following requirements has been recently proposed. It is testable with GW observations, it is consistent with other experiments, including short distance tests of GR, it agrees with widely accepted principles of physics, such as locality, causality and unitarity, and it does not involve new light degrees of freedom. The most general theory satisfying these requirements corresponds to adding to the GR Lagrangian operators constructed out of powers of the Riemann tensor, suppressed by a scale comparable to the curvature of the observed merging binaries. The presence of these operators modifies the metric corresponding to black hole solutions, the gravitational potential between compact objects, as well as their effective mass and current quadrupoles, ultimately correcting the waveform of the emitted GW. I will report on the status of the development of this theory and on the current constraints on its parameters as obtained from GW observations.