Testing the strong-field regime of gravity has become of great interest in the scientific community following the first gravitational wave detections and growing indications that General Relativity (GR) may require modifications in extreme environments.
In this context, black holes are remarkably simple yet powerful laboratories, providing a unique opportunity to search for deviations from GR and to constrain extensions of gravity in extreme conditions.
A natural framework to explore such deviations is through the inclusion of additional scalar degrees of freedom. Among them, scalar–Gauss–Bonnet (sGB) gravity offers a well-motivated framework, emerging naturally from fundamental high-energy theories such as string theory.
While most existing studies have focussed on massless versions of this theory, introducing a scalar field mass is crucial for a more realistic description and may uncover novel dynamical features.
Motivated by these considerations, I will present recent black hole simulations in massive sGB theory obtained using Numerical Relativity (NR), a rapidly expanding field that has only recently enabled fully non-linear, dynamical studies of compact objects beyond General Relativity and whose full potential is still being explored.
I will first focus on the role of the scalar mass in the spacetime dynamics, as well as the effects of massive scalar perturbations in isolated black holes in the context of quasinormal-mode spectroscopy.
Building on this groundwork, I will then introduce preliminary results from fully dynamical black hole merger simulations in massive sGB gravity, a regime that to date has seen only limited exploration and remains largely unexplored in the massive scalar case.