Revisiting the Brans solutions of scalar-tensor gravity

Faraoni, Valerio; Hammad, Fayçal; Belknap-Keet, Shawn D.

doi:10.1103/physrevd.94.104019

Cited by 33 publications

(47 citation statements)

References 65 publications

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“…which is in agreement with the previously obtained result in [27]. To summarise for the branch ǫ > 0, if γ = ±1 the spherically symmetric solutions reduce to the Schwarzschild solution with a constant scalar field, while if γ = 1 then we have a naked singularity when the parameter ν does not satisfy the bound (3.77), and a wormhole solution otherwise.…”

Section: Areal Radius and Ricci Scalarsupporting

confidence: 91%

“…Thus the region near ρ = ρ o e K +1 e K −1 is asymptotically large in the sense that the proper area of a circle at radius ρ, A(ρ) = 4πr(ρ) 2 , goes to infinity as one approaches that region but not asymptotically flat, making the wormhole asymmetric under the interchange of the two asymptotic regions. This feature is also exhibited in Brans Class I solution for a specific range of its parameters (see [26], [27] for more details). Also, notice that even though it is not evident from the form of (3.51), the parameter ν determines the behaviour of b(r) as it is hidden inside ρ(r), the inverse of (3.39).…”

Section: B ′ (R) < B(r)mentioning

confidence: 73%

“…The requirement that the scalar fieldφ, in the Einstein frame, is real implies α > 0 (ω > − 3 2 in D=4) hence, only Brans Class I solution can be obtained in the Jordan frame. However, there are other three classes of Brans solutions which correspond to ω < − 3 2 (for a detailed discussion on the Brans solutions see the review [27].…”

Section: )mentioning

confidence: 99%

“…It was further proved in [25] that the static spherically symmetric solutions of BD theory describe either wormholes or naked singularities. A more extensive study was performed in [27] where it was shown that, the static and spherically symmetric BD solutions of scalar-tensor gravity, analyzed in both the Jordan and the Einstein conformal frames, describe wormholes, naked singularities or the Schwarzschild solution. Thus, they do not describe black hole solutions besides those in GR.…”

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confidence: 99%

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Wormhole solutions in modified Brans-Dicke theory

Papantonopoulos

Vlachos

2020

Phys. Rev. D

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We consider a modified Brans-Dicke theory in which except the usual Brans-Dicke parameter a new dimensionful parameter appears which modifies the kinetic term of the scalar field coupled to gravity. Solving the coupled Einstein-Klein-Gordon equations we find new spherically symmetric solutions. Depending on the choices of the parameters these solutions reduce to the Schwarzschild solution of General Relativity and they give new wormhole solutions which depend on the new parameter.PACS numbers: I. INTRODUCTIONScalar fields play an important role in the General Relativity (GR) on short and large distances. On short distances they are dressing the local black hole solutions with scalar hair and they provide wormhole solutions while on large distances they describe the early inflationary universe and also its late-times cosmic evolution. In a attempt to provide a viable theory of gravity and to cure certain inconsistencies of GR, scalar-tensor theories were introduced. As it is well known, Brans-Dicke theory (BD) [1] is one of the first scalar-tensor gravity theories that modifies GR in a viable way and respects Mach's principle and weak equivalence principle (WEP). In this theory there is an effective Newtonian gravitational constant G which is the inverse of the scalar field, G ∼ 1 φ . It is characterized by a new dimensionless coupling constant ω large values of which mean a significant contribution from the tensor part, while scalar field contribution is important for small values. GR is recovered in the limit ω → ∞.It is interesting to note that BD theory appears in supergravity models such as in string theory at low-energies or in the Kaluza-Klein theories after a dimensional reduction process [2]. These theories yield the correct Newtonian weak-field limit, but care should be taken when one studies these theories and compare their predictions with GR. In general scalar fields, depending on their coupling to gravity, mediate fifth forces. In the case of BD solar system measurements of post-Newtonian corrections require that ω is larger than a few thousands [3]. Therefore in these theories scalar fields should accommodate a mechanism to suppress the scalar interaction on small scales. There are various screening mechanisms to suppress scalar interactions on small scales. One of the basic screening mechanism is the Vainshtein mechanism [4] which was developed for the massive gravity (for an extensive review on the Vainshtein mechanism in massive gravity see [5]).On large scales, ω gets substantially lower values in a model dependent way [6], from cosmological observations. On the other side, the gravitational coupling may depends on the scale [7], having different value at local and at cosmological scale. In this case ω can be smaller at cosmological scales giving deviations from GR, while agreement with local tests is preserved. Special solutions on BD cosmology have been given in [8] which are generalizations of the dust solution first given by Brans-Dicke. In [9] special radiation solutions for spatially curve...

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Section: Areal Radius and Ricci Scalarsupporting

confidence: 91%

Section: B ′ (R) < B(r)mentioning

confidence: 73%

Section: )mentioning

confidence: 99%

mentioning

confidence: 99%

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Wormhole solutions in modified Brans-Dicke theory

Papantonopoulos

Vlachos

2020

Phys. Rev. D

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“…However, it is to be remarked that spin is an important factor and many astrophysical observations of black holes are inconsistent with the Schwarzschild metric 6 . A glimpse of such inconsistency is provided by the observed radio variability in the emission spectrum from SgrA * believed to be induced by a small spin of an assumed Kerr black hole [13].…”

Section: Discussionmentioning

confidence: 99%

Ring-down gravitational waves and lensing observables: How far can a wormhole mimic those of a black hole?

Nandi¹,

Izmailov²,

Yanbekov³

et al. 2017

Phys. Rev. D

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It has been argued that the recently detected ring-down gravity waveforms could be indicative only of the presence of light rings in a horizonless object, such as a surgical Schwarzschild wormhole, with the frequencies differing drastically from those of the horizon quasinormal mode frequencies ω QNM at late times. While the possibility of such a horizonless alternative is novel by itself, we show by the example of Ellis-Bronnikov wormhole that the differences in ω QNM in the eikonal limit (large l) need not be drastic. This result will be reached by exploiting the connection between ω QNM and the Bozza strong field lensing parameters. We shall also show that the lensing observables of the EllisBronnikov wormhole can also be very close to those of a black hole (say, SgrA * hosted by our galaxy) of the same mass. This situation indicates that the ringdown frequencies and lensing observables of the Ellis-Bronnikov wormhole can remarkably mimic those of a black hole. The constraint on wormhole parameter γ imposed by experimental accuracy is briefly discussed. We also provide independent arguments supporting the stability of the Ellis-Bronnikov wormhole proven recently.---------------

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Orbiting naked singularities in large- $$\omega $$ ω Brans–Dicke gravity

Chauvineau

2017

Gen Relativ Gravit

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Revisiting the Brans solutions of scalar-tensor gravity

Cited by 33 publications

References 65 publications

Wormhole solutions in modified Brans-Dicke theory

Wormhole solutions in modified Brans-Dicke theory

Ring-down gravitational waves and lensing observables: How far can a wormhole mimic those of a black hole?

Orbiting naked singularities in large- $$\omega $$ ω Brans–Dicke gravity

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