Gravitation Due to Scalar Potentials and Black Holes

Scalar Black Holes

A class of exact regular spherically symmetric solutions to the Einstein equation obeying Dymnikova’s definition T 1 1 = T 0 0 of vacuumlike state is considered. These solutions, that may be interpreted as black holes, are not only singularity free, but also do not set us thinking about the loss of information under gravitational collapse. However, according to the singularity theorems, the geo...

Masses of Stellar Black Holes and Testing Theories of Gravitation

The paper analyzes the mass distribution of stellar black holes derived from the light and radialvelocity curves of optical stars in close binary systems using dynamical methods. The systematic errors inherent in this approach are discussed. These are associated primarily with uncertainties in models for the contribution from gaseous structures to the optical brightness of the systems under con...

Cold Black Holes in Scalar-tensor Theories

We study the possible existence of black holes in scalar-tensor theories of gravity in four dimensions. Their existence is verified for anomalous versions of these theories, with a negative kinetic term in the Lagrangian. The Hawking temperature TH of these holes is zero, while the horizon area is (in most cases) infinite. It is shown that an infinite value of TH can occur only at a curvature s...

Charged black holes with scalar hair.

Static black holes in scalar tensor gravity

We study static black hole solutions in scalar tensor gravity. We present exact solutions in hiperextended models with a quadratic scalar potential. On leave from: Departamento de F́ısica da Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal