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

Understand

We construct exact, time-dependent, black hole solutions of Einstein-Maxwell-dilaton theory with arbitrary dilaton coupling, $a$.

• For $a=1$ this theory arises as the four-dimensional 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 $a=1$ 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.