Black holes in the Universe: Generalized Lemaître-Tolman-Bondi solutions

Abstract

We present new exact solutions which presumably describe black holes in the background of a spatially flat, pressureless dark matter (DM)-, or dark matter plus dark energy (DM+DE)-, or quintom-dominated universe. These solutions generalize Lemaître-Tolman-Bondi metrics. For a DM-or (DM+DE)-dominated universe, the area of the black hole apparent horizon (AH) decreases with the expansion of the universe while that of the cosmic AH increases. However, for a quintomdominated universe, the black hole AH first shrinks and then expands, while the cosmic AH first expands and then shrinks. A (DM+DE)-dominated universe containing a black hole will evolve to the Schwarzschild-de Sitter solution with both AHs approaching constant size. In a quintomdominated universe, the black hole and cosmic AHs will coincide at a certain time, after which the singularity becomes naked, violating Cosmic Censorship.

Inhomogeneous universe in f(T) theory

“…Through a set of non-diagonal tetrads we still were able to make various analysis already made in the GR, as the evolution of the black holes apparent horizon (AH) and cosmic AH [23], CMB [11,27] and many other possibilities, but which will be minutely addressed in a future work. Hence, we make possible the analysis of the other usual cosmological and astrophysical phenomena, already realized in the GR, but which still have some obscure points to be explained.…”

“…where d(r) is an algebraic function of r. Putting d(r) = r 3/2 and M D (r) = 8πρ 0 r 3 /3, wherē ρ 0 is a constant, we re-obtain the equations of Friedmann for an universe dominated by the matter [23], where A(r, t) = ra(t), a(t)…”

Inhomogeneities in Cosmological “Backgrounds” in Einstein Theory

“…Apparent and trapping horizons were studied also in Oppenheimer-Schneider, Vaidya, and Lemaître-Tolman-Bondi spacetimes [13,67]. In this last class of models, in particular, the use of different coordinates determines different foliations and, potentially, different apparent horizons.…”

Phantom accretion by black holes and the generalized second law of thermodynamics

“…On the other hand, Gao and collaborators [22] claimed that the back-reaction provoked by the accretion of phantom matter on the black hole metric was ignored in the mentioned calculations. In a low matter density background, this effect can be safely ignored, but if the background matter density is large (comparable to the black hole density), the metric describing this black hole will be significantly modified, and the backreaction must necessarily be considered.…”