Gravitational collapse and formation of universal horizons in Einstein-aether theory

Understand

We numerically study the gravitational collapse of a massless scalar field with spherical symmetry in Einstein-aether theory, and show that apparent, spin-0 and dynamical universal horizons (dUHs) can be all formed.

• The spacetime and the aether field are well-behaved and regular, including regions nearby these horizons (but away from the center of spherical symmetry).
• The spacetime outside the apparent and spin-0 horizons settles down to a static configuration, and some of such resulting static black holes were already found numerically in the literature.
• On the other hand, the proper distance of the outermost dUH from the apparent (or spin-0) horizon keeps increasing on $\mbox{\ae}$ther-orthogonal time slices.