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

Black holes in multi-fractional and Lorentz-violating models

We study static and radially symmetric black holes in the multi-fractional theories of gravity with q-derivatives and with weighted derivatives, frameworks where the spacetime dimension varies with the probed scale and geometry is characterized by at least one fundamental length [Formula: see text]. In the q-derivatives scenario, one finds a tiny shift of the event horizon. Schwarzschild black ...

Dilaton gravity black holes with regular interior

In a one parameter family of dilaton gravity theories which allow the coupling of the dilaton to gravity and to a U(1) gauge field to differ, we have found the existence of everywhere regular spacetimes describing black holes hiding expanding universes inside their horizon.

Bigravity and Lorentz-violating Massive Gravity

Bigravity is a natural arena where a non-linear theory of massive gravity can be formulated. If the interaction between the metrics f and g is non-derivative, spherically symmetric exact solutions can be found. At large distances from the origin, these are generically Lorentz-breaking bi-flat solutions (provided that the corresponding vacuum energies are adjusted appropriately). The spectrum of...

Black holes with regular horizons in Maxwell - scalar gravity .

A class of exact static spherically symmetric solutions of the Einstein-Maxwell gravity coupled to a massless scalar field has been obtained in harmonic coordinates of the Minkowski space-time. For each value of the coupling constant a, these solutions are characterized by a set of three parameters, the physical mass μ0, the electric charge Q0 and the scalar field parameter k. We have found tha...

General Relativity and Compact Objects – Neutron Stars and Black Holes