Unveiling compact objects with ultracold atoms

Black holes and neutron stars are the most extreme objects in the universe, serving as natural laboratories for probing fundamental physics under conditions of intense gravity, density, and magnetic fields. Observational access to these compact objects is primarily achieved through gravitational waves, electromagnetic, and neutrino emissions, which provide valuable constraints on their properties, but still with limited information about their internal structure. Furthermore, a comprehensive theoretical framework capable of fully characterizing them remains still incomplete. Despite remarkable progress in observational astronomy, the intrinsic irreproducibility and inaccessibility of compact objects continue to pose major challenges for their exhaustive characterization. A valuable alternative is to simulate their behavior in controlled laboratory settings. Ultracold atoms offer one of the most promising platforms for this purpose. In recent years, ultracold atomic physics faced a huge development that improved experimental control to manipulate atoms at very low temperature. In the nanoKelvin range, the quantum mechanical nature of the atoms is manifest and gives rise to macroscopic effects. In this regime, phase transitions– from disordered thermal phase to ordered ones– are experimentally observed. By carefully tuning the control parameters of these systems, we can access phases that emulate those realized in compact objects. In this way, we can theoretically investigate two key phenomena: the predicted universal lower bound of the ratio between the shear viscosity and the entropy density at the event horizon of black holes, and the dynamics of vortices inside neutron stars during a glitch event.