Abstract
We classified and studied the charged black hole and wormhole solutions in the Einstein–Maxwell system in the presence of a massless, real scalar field. The possible existence of charged black holes in general scalar–tensor theories was studied in Bronnikov et al., 1999; black holes and wormholes exist for a negative kinetic term for the scalar field. Using a conformal transformation, the static, spherically symmetric possible structures in the minimal coupled system are described. Besides wormholes and naked singularities, only a restricted class of black hole exists, exhibiting a horizon with an infinite surface and a timelike central singularity. The black holes and wormholes defined in the Einstein frame have some specificities with respect to the non-minimal coupling original frame, which are discussed in the text.
Highlights
Black holes (BHs) are objects predicted by the general relativity (GR) theory
To complement the analysis presented in [14], our goal was to stress the properties of the solutions with their physical content and the role played by the conformal transformation, and its main consequences, in passing from the Jordan to the Einstein frame
In this work, the black hole and wormhole configurations of the Einstein– Maxwell system with a massless scalar field. Such a structure can be obtained from the Brans–Dicke theory in the presence of the Maxwell field by a conformal transformation
Summary
Black holes (BHs) are objects predicted by the general relativity (GR) theory. Their main characteristic feature is the existence of an event horizon, a hypersurface separating two regions, the internal one, which generally contains a singularity, and the external one with the asymptotic spatial infinity where the observer may be located. The BH solutions belong to the so-called cold BHs: the horizon has an infinite area, and its corresponding Hawking temperature is zero They are in general unstable [15], even if they present some interesting causal structures. Universe 2022, 8, 151 are only two possible classes of BHs, one with a double horizon and another one with a single horizon, characteristics similar to the Reissner–Nordström BH, non-extreme and extreme In both cases, the central singularity is timelike (repulsive), which may again be related to the presence of the Maxwell field. The central singularity is timelike (repulsive), which may again be related to the presence of the Maxwell field Both solutions are cold black holes, which may be related to the presence of a (phantom) scalar field.
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