Ray tracing Einstein-Æther black holes: Universal versus Killing horizons

  title={Ray tracing Einstein-{\aE}ther black holes: Universal versus Killing horizons},
  author={Bethan Cropp and Stefano Liberati and Arif Mohd and Matt Visser},
  journal={Physical Review D},
Violating Lorentz invariance, and so implicitly permitting some form of super-luminal communication, necessarily alters the notion of a black hole. Nevertheless, in both Einstein-\ae{}ther gravity and Ho\ifmmode \check{r}\else \v{r}\fi{}ava-Lifshitz gravity, there is still a causally disconnected region in black-hole solutions, now being bounded by a ``universal horizon,'' which traps excitations of arbitrarily high velocities. To better understand the nature of these black holes, and their… 

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