Regular black holes and horizonless ultra-compact objects in Lorentz-violating gravity

There is growing evidence that Horava gravity may be a viable quantum theory of gravity. It is thus legitimate to expect that gravitational collapse in the full, non-projectable version of the theory should result in geometries that are free of space-time singularities. Previous analyses have shown that such geometries must belong to one of the following classes: simply connected regular black holes with inner horizons; non-connected black holes hiding a wormhole mouth (black bounces); simply connected or non-connected horizonless compact objects. Here, we consider a singular black hole in the low-energy limit of non-projectable Horava gravity, i.e. khronometric theory, and describe examples of its possible regularisations, covering all of the viable classes. To our knowledge, these examples constitute the first instances of black holes with inner universal horizons, of black bounces and of stars with a de Sitter core in the context of Lorentz-violating theories of gravity.

Automated summary

There is increasing evidence that Horava gravity is a viable quantum theory of gravity. This suggests that gravitational collapse in the non-projectable version of the theory should result in geometries without space-time singularities. Previous studies have identified different classes of such geometries, including regular black holes, non-connected black holes with wormhole mouths, and horizonless compact objects. This study focuses on a singular black hole in the low-energy limit of non-projectable Horava gravity, exploring examples of its regularizations within all viable classes. These examples are the first instances of black holes with inner universal horizons, black bounces, and stars with a de Sitter core in the context of Lorentz-violating theories of gravity.