J. C. Fabris

Neutron Stars in Rastall Gravity

We calculate static and spherically symmetric solutions for the Rastall modification of gravity to describe Neutron Stars (NS). The key feature of the Rastall gravity is the non-conservation of the energy-momentum tensor proportionally to the space-time curvature. Using realistic equations of state for the NS interior we place a bound on the non-GR behaviour of the Rastall theory which should be

Static, spherically symmetric solutions with a scalar field in Rastall gravity

\lesssim 0.1\%

Generalisation for regular black holes on general relativity to f ( R ) gravity

level. This work presents the more stringent contraints on the deviations of GR caused by the Rastall proposal.

On horizons and wormholes in k-essence theories

Rastall’s theory belongs to the class of non-conservative theories of gravity. In vacuum, the only non-trivial static, spherically symmetric solution is the Schwarzschild one, except for a very special case. When a canonical scalar field is coupled to the gravity sector in this theory, new exact solutions appear for some values of the Rastall parameter a. Some of these solutions describe the same space–time geometry as the recently found solutions in the k-essence theory with a power function for the kinetic term of the scalar field. There is a large class of solutions (in particular, those describing wormholes and regular black holes) whose geometry coincides with that of solutions of GR coupled to scalar fields with nontrivial self-interaction potentials; the form of these potentials, however, depends on the Rastall parameter a. We also note that all solutions of GR with a zero trace of the energy-momentum tensor, including black-hole and wormhole ones, may be re-interpreted as solutions of Rastall’s theory.

Cosmology from a new nonconservative gravity

In this paper, we determine regular black hole solutions using a very general f(R) theory, coupled to a non-linear electromagnetic field given by a Lagrangian

The final state of gravitational collapse in Eddington‐inspired Born‐Infeld theory

\mathcal {L}_\mathrm{NED}

Newtonian hydrodynamic equations with relativistic pressure and velocity

LNED. The functions f(R) and