Challenging cosmic censorship in Einstein-Maxwell-scalar theory with numerically simulated gedanken experiments

We perform extensive nonlinear numerical simulations of the spherical collapse of (charged) wave packets onto a charged black hole within Einstein-Maxwell theory and in Einstein-Maxwell-scalar theory featuring nonminimal couplings and a spontaneous scalarization mechanism. We confirm that black holes in full-fledged Einstein-Maxwell theory cannot be overcharged past extremality and no naked singularities form, in agreement with the cosmic censorship conjecture. We show that naked singularities do not form even in Einstein-Maxwell-scalar theory, although it is possible to form scalarized black holes with charge above the Reissner-Nordström bound. We argue that charge and mass extraction due to superradiance at the fully nonlinear level is crucial to bound the charge-to-mass ratio of the final black hole below extremality. We also discuss some "descalarization"mechanisms for scalarized black holes induced either by superradiance or by absorption of an opposite-charged wave packet; in all cases the final state after descalarization is a subextremal Reissner-Nordström black hole.