Tests of Cosmic Censorship in the Ernst Spacetime

The Ernst spacetime is a solution of the Einstein-Maxwell equations describing two charged black holes accelerating apart in a uniform electric (or magnetic) field. As the field approaches a critical value, the black hole horizon appears to touch the acceleration horizon. We show that weak cosmic censorship cannot be violated by increasing the field past this critical value: The event horizon remains intact. On the other hand, strong cosmic censorship does appear to be violated in this spacetime: For a certain range of parameters, we find evidence that the inner horizon is classically stable.