Scalarized Black Holes in Teleparallel Gravity

Bahamonde, Sebastian; Ducobu, Ludovic; Pfeifer, Christian

doi:10.48550/arxiv.2201.11445

“…Hence, all of these solutions might not be so physically interesting since they cannot describe black holes nor standard astrophysical systems. Two recent papers found the first non-trivial exact black hole solutions in f(T, B) gravity and also in teleparallel scalar-tensor theories [641,642]. These solutions are based on the complex tetrad in equation (5.153).…”

Section: Spherical Symmetry and Solutionsmentioning

confidence: 99%

Teleparallel gravity: from theory to cosmology

Bahamonde

¹

,

Dialektopoulos

²

,

Escamilla-Rivera

³

et al. 2023

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Teleparallel gravity has significantly increased in popularity in recent decades, bringing attention to Einstein’s other theory of gravity. In this Review, we give a comprehensive introduction to how teleparallel geometry is developed as a gauge theory of translations together with all the other properties of gauge field theory. We also related this form of geometry to the broader metric-affine approach to forming gravitational theories where we describe a systematic way of constructing consistent teleparallel theories that respect certain physical conditions such as local Lorentz invariance. We first use teleparallel gravity to formulate a teleparallel equivalent of general relativity which is dynamically equivalent to general relativity but which may have different behaviors for other scenarios, such as quantum gravity. After setting this foundation, we describe the plethora of modified teleparallel theories of gravity that have been proposed in the literature. We attempt to connect them together into general classes of covariant gravitational theories. Of particular interest, we highlight the recent proposal of a teleparallel analogue of Horndeski gravity which offers the possibility of reviving all of the regular Horndeski contributions. In the second part of the Review, we first survey works in teleparallel astrophysics literature where we focus on the open questions in this regime of physics. We then discuss the cosmological consequences for the various formulations of teleparallel gravity. We do this at background level by exploring works using various approaches ranging from dynamical systems to Noether symmetries, and more. Naturally, we then discuss perturbation theory, firstly by giving a concise approach in which this can be applied in teleparallel gravity theories and then apply it to a number of important theories in the literature. Finally, we examine works in observational and precision cosmology across the plethora of proposal theories. This is done using some of the latest observations and is used to tackle cosmological tensions which may be alleviated in teleparallel cosmology. We also introduce a number of recent works in the application of machine learning to gravity, we do this through deep learning and Gaussian processes, together with discussions about other approaches in the literature.

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“…Teleparallel geometry is also the basis for other manifestations of teleparallel gravity theories such as New General Relativity [20,21], f (T, B) gravity [22] (B represents the difference between the Ricci and torsion scalars and is a boundary term) and f (T, T G ) gravity [23][24][25] (T G represents the teleparallel analogue of the Gauss-Bonnet term). There has also been a significant amount of work exploring possible scalar-tensor extensions of TG [26][27][28][29][30][31][32][33][34] including the coupling of pseudo-scalars (axions) [35,36].…”

Section: Introductionmentioning

confidence: 99%

Perturbations in non-flat cosmology for f(T) gravity

Bahamonde

¹

,

Dialektopoulos

²

,

Hohmann

³

et al. 2023

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The study of cosmological perturbation theory in f(T) gravity is a topic of great interest in teleparallel gravity since this is one of the simplest generalizations of the theory that modifies the teleparallel equivalent of general relativity. In this work, we explore the possibility of a non-flat FLRW background solution and perform perturbations for positively as well as negatively curved spatial geometries, together with a comparison to the flat case. We determine the generalized behaviour of the perturbative modes for this non-flat FLRW setting for arbitrary f(T) models, when the most general homogeneous and isotropic background tetrads are used. We also identify propagating modes in this setup, and relate this with the case of a flat cosmology.

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“…These two exact black solutions represent the first non-trivial ones in the literature of teleparallel gravity. In the context of scalartorsion theories, recently, new exact scalarized black hole solutions were obtained in [96].…”

Section: Introductionmentioning

confidence: 99%

Testing Born–Infeld f(T) teleparallel gravity through Sgr $$\hbox {A}^\star $$ observations

Jusufi

¹

,

Capozziello

²

,

Bahamonde

³

et al. 2022

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We use observational data from the S2 star orbiting around the Galactic Center to constrain a black hole solution of extended teleparallel gravity models. Subsequently, we construct the shadow images of Sgr $$\hbox {A}^{\star }$$ A ⋆ black hole. In particular, we constrain the parameter $$\alpha =1/\lambda $$ α = 1 / λ which appears in the Born–Infeld f(T) model. In the strong gravity regime we find that the shadow radius increases with the increase of the parameter $$\alpha $$ α . Specifically, from the S2 star observations, we find within $$1\sigma $$ 1 σ that the parameter must lie between $$0 \le \alpha /M^2 \le 6 \times 10^{-4}$$ 0 ≤ α / M 2 ≤ 6 × 10 - 4 . Consequently, we used the best fit parameters to model the shadow images of Sgr $$\hbox {A}^{\star }$$ A ⋆ black hole and then using the Gauss-Bonnet theorem we analysed the deflection angle for leading order expansions of the parameter $$\alpha $$ α . It is found that within the parameter range, these observables are very close to the Schwarzschild case. Furthermore, using the best fit parameters for the Born–Infeld f(T) model we show that the angular diameter is consistent with recent observations for the Sgr $$\hbox {A}^{\star }$$ A ⋆ with angular diameter $$(51.8 \pm 2.3) \mu $$ ( 51.8 ± 2.3 ) μ arcsec and difficult to be distinguished from the GR. For the deflection angle of light, in leading order terms, we find that the deflection angle expressed in the ADM mass coincides with the GR, but the ADM mass in the Born–Infeld f(T) gravity increases with the increase of $$\alpha $$ α and the overall deflection angle is expected to me greater in f(T) gravity. As a consequence of this fact, we have shown that the electromagnetic intensity observed in shadow images is smaller compared to GR.

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Scalarized Black Holes in Teleparallel Gravity

Cited by 5 publications

References 64 publications

Teleparallel gravity: from theory to cosmology

Teleparallel gravity: from theory to cosmology

Perturbations in non-flat cosmology for f(T) gravity

Testing Born–Infeld f(T) teleparallel gravity through Sgr $$\hbox {A}^\star $$ observations

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