GJC: Fabrizio Corelli "Hyperbolicity in scalar-Gauss-Bonnet with Ricci coupling: a review of the recent studies by Thaalba et al."

Wednesday 6 Nov 2024, 13:00 → 14:00 Europe/Rome

Sala Lauree (Marconi)

When constructing modified theories of gravity, hyperbolicity is a crucial property to put under scrutiny. It ensures that physical information propagates at finite speed and that the theory is predictive.
Remarkably Einstein-scalar-Gauss-Bonnet (EsGB), one of the most studied modified gravity theories, has been shown to lose hyperbolicity in scenarios like the gravitational collapse. However, the introduction of new terms in the action can alter the structure of the field equations, possibly rendering them hyperbolic.
In this respect one of the candidate theories is the scalar-Gauss-Bonnet gravity with a Ricci coupling. Here a real scalar field is nonminimally coupled both to the Gauss-Bonnet invariant and to the Ricci scalar, via coupling functions that can be different from each other. In a series of three papers [https://arxiv.org/pdf/2306.01695, https://arxiv.org/pdf/2409.11398, https://arxiv.org/pdf/2410.16264] Thaalba, Franchini, Bezares and Sotiriou investigated the character of the field equations in this theory by means of fully-nonlinear numerical simulations in spherical symmetry.
After a brief introduction on hyperbolicity I will discuss the recent studies by Thaalba et al.