Wormholes and naked singularities in Brans–Dicke cosmology

Abstract

We perform analytical and numerical study of static spherically symmetric solutions in the context of Brans-Dicke-like cosmological model by Elizalde et al. [1] with an exponential potential. In this model the phantom regime arises without the appearance of any ghost degree of freedom due to the specific form of coupling. For the certain parameter ranges the model contains a regular solution which we interpret as a wormhole in an otherwise dS Universe. We put several bounds on the parameter values: ω < 0, α 2 /|ω| < 10 −5 , 22.7 φ 0 25 . The numerical solution could mimic the Schwarzschild one, so the original model is consistent with astrophysical and cosmological observational data. However differences between our solution and the Schwarzschild one can be quite large, so black hole candidate observations could probably place further limits on the φ 0 value.

Linearized modified gravity theories with a cosmological term: advance of perihelion and deflection of light

“…Here, V (φ) plays the role of a variable cosmological term and when φ is set to a constant, the action (3) also reduces to GRΛ theory. There are various works considering the addition of such a potential term and its various implications to BD theory [23,27,35,36,[51][52][53][54][55] in various contexts. In general BDΛ and BDV theories and also all possible BDV theories having different potentials may have different characteristics and lead to different physics.…”

Horndeski scalar-tensor black hole geodesics

“…This is the situation that to our knowledge did not appear before in extended gravity solutions: usually we can always suppress the deviations from the GR by the fine tuning. Another interesting example, demonstrating that studying local spherically symmetric solutions can provide useful information on cosmological models is given in [21]. The paper implements some PPN-based bounds on the model parameters due to the black hole-like metric for the framework, initially constructed for cosmological purposes.…”

Massless charged particles, naked singularity, and GUP in Reissner-Nordström-de Sitter-like spacetime

“…Another line of research that deals with this conjecture is to see its topological effects together with null energy condition [35][36][37][38][39][40][41][42][43][44][45][46][47][48]. Also there is another debate about the validity of either cosmic censorship conjecture or naked singularities in modified gravity theories upon considering null energy condition [49][50][51][52][53][54][55][56][57]. Recent analytical proof [58] is in favor of cosmic censorship conjecture, while others [59][60][61] counter-argued cosmic censorship conjecture, leaving the quest unanswered.…”