Radiating black holes in Einstein-Maxwell-dilaton theory and cosmic censorship violation

Pedro Aniceto, Paolo Pani, Jorge V. Rocha
2016 Journal of High Energy Physics  
We construct exact, time-dependent, black hole solutions of Einstein-Maxwelldilaton theory with arbitrary dilaton coupling, a. For a = 1 this theory arises as the fourdimensional low-energy effective description of heterotic string theory. These solutions represent electrically charged, spherically symmetric black holes emitting or absorbing charged null fluids and generalize the Vaidya and Bonnor-Vaidya solutions of general relativity and of Einstein-Maxwell theory, respectively. The a = 1
more » ... vely. The a = 1 case stands out as special, in the sense that it is the only choice of the coupling that allows for a time-dependent dilaton field in this class of solutions. As a by-product, when a = 1 we show that an electrically charged black hole in this theory can be overcharged by bombarding it with a stream of electrically charged null fluid, resulting in the formation of a naked singularity. This provides an example of cosmic censorship violation in an exact dynamical solution to low-energy effective string theory and in a case in which the total stress-energy tensor satisfies all energy conditions. When a = 1, our solutions necessarily have a time-independent scalar field and consequently cannot be overcharged.
doi:10.1007/jhep05(2016)115 fatcat:3w7f6bwacvafrljcgg7czdvt4y