Slowly moving black holes in khrono-metric model

Abstract

We search for solutions describing slowly moving non-rotating black holes in the khrono-metric model, a modified gravity theory with preferred time (khronon) which arises at low energies from the non-projectable Horava gravity. We work in the decoupling limit when the back-reaction of the khronon on the metric is small and can be treated perturbatively. For a given black hole velocity, we find a family of solutions parameterized by the khronon propagation speed and regular everywhere outside the universal horizon. On the universal horizon they have a weak singularity manifesting itself in a non-analyticity of the khronon field. Using the behavior of khronon at infinity we extract the leading black hole sensitivity for which we obtain a simple analytic expression valid throughout the phenomenologically allowed parameter space.