Traversable Morris–Thorne–Buchdahl wormholes in quadratic gravity

Nguyen, Hoang Ky; Azreg‐Aïnou, Mustapha

doi:10.1140/epjc/s10052-023-11805-3

Cited by 14 publications

(14 citation statements)

References 67 publications

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“…Expression (24) is a special case of the generalized Campanelli-Lousto solution that we reported for Brans-Dicke gravity [22]. This relationship between the two solutions further highlights the shared characteristics of pure  gravity and Brans-Dicke gravity.…”

Section: Buchdahl-inspired Solutionssupporting

confidence: 58%

“…The metric given in equation (22) possesses two additional noteworthy properties: (I) Non-triviality of the asymptotically flat Buchdahl-inspired metric: The metric in (22) is Ricci-scalar flat, viz. º " Î +  r 0  .…”

Section: Buchdahl-inspired Solutionsmentioning

confidence: 99%

“…(II) Embedding into the generalized Campanelli-Lousto solution of Brans-Dicke gravity: Furthermore, it has been shown in [21,22] that the metric in ( 22) is equivalent to…”

Section: Buchdahl-inspired Solutionsmentioning

confidence: 99%

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A stationary axisymmetric vacuum solution for pure ² gravity

Azreg-Aïnou,

Ky Nguyen

2023

Phys. Scr.

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The closed-form expression for pure  2 vacuum solution obtained in Phys. Rev. D 107, 104 008 (2023) lends itself to a generalization to axisymmetric setup via the modified Newman–Janis algorithm. We adopt the procedure put forth in Phys. Rev. D 90, 064 041 (2014) bypassing the complexification of the radial coordinate. The procedure presumes the existence of Boyer-Lindquist coordinates. Using the Event Horizon Telescope Collaboration results, we model the central black hole M87* by the thus obtained exact rotating metric, depending on the mass, rotation parameter and a third dimensionless parameter. The latter is constrained upon investigating the shadow angular size assuming mass and rotation parameters are those of M87*. Stability is investigated.

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Section: Buchdahl-inspired Solutionssupporting

confidence: 58%

Section: Buchdahl-inspired Solutionsmentioning

confidence: 99%

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A stationary axisymmetric vacuum solution for pure ² gravity

Azreg-Aïnou,

Ky Nguyen

2023

Phys. Scr.

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“…This latter solution is asymptotically de Sitter, and is specified by four parameters, reflecting the fourth-derivative nature of a quadratic theory). Upon another coordinate transformation [22] 1 −…”

Section: The Special Buchdahl-inspired Metric: Brief Reviewmentioning

confidence: 99%

“…The metric is dependent on a new (Buchdahl) parameter k of higher-derivative characteristic, and recovers the Schwarzschild metric when k = 0. In a recent work [22], it was demonstrated that the special Buchdahl-inspired metric supports a two-way traversable Morris-Thorne-Buchdahl (MTB) wormhole for k ∈ (−1, 0), in which case the weak energy condition is formally violated.…”

Section: Introductionmentioning

confidence: 99%

Closed Timelike Curves Induced by a Buchdahl-Inspired Vacuum Spacetime in R2 Gravity

Nguyen,

Lobo

2023

Universe

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The recently obtained special Buchdahl-inspired metric Phys. Rev. D 107, 104008 (2023) describes asymptotically flat spacetimes in pure Ricci-squared gravity. The metric depends on a new (Buchdahl) parameter k˜ of higher-derivative characteristic, and reduces to the Schwarzschild metric, for k˜=0. For the case k˜∈(−1,0), it was shown that it describes a traversable Morris–Thorne–Buchdahl (MTB) wormhole Eur. Phys. J. C 83, 626 (2023), where the weak energy condition is formally violated. In this paper, we briefly review the special Buchdahl-inspired metric, with focuses on the construction of the Kruskal–Szekeres (KS) diagram and the situation for a wormhole to emerge. Interestingly, the MTB wormhole structure appears to permit the formation of closed timelike curves (CTCs). More specifically, a CTC straddles the throat, comprising of two segments positioned in opposite quadrants of the KS diagram. The closed timelike loop thus passes through the wormhole throat twice, causing two reversals in the time direction experienced by the (timelike) traveller on the CTC. The key to constructing a CTC lies in identifying any given pair of antipodal points (T,X) and (−T,−X) on the wormhole throat in the KS diagram as corresponding to the same spacetime event. It is interesting to note that the Campanelli–Lousto metric in Brans–Dicke gravity is known to support two-way traversable wormholes, and the formation of the CTCs presented herein is equally applicable to the Campanelli–Lousto solution.

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On the degrees of freedom of R2 gravity in flat spacetime

Hell,

Lüst,

Zoupanos

2024

J. High Energ. Phys.

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We study the degrees of freedom of R2 gravity in flat spacetime with two approaches. By rewriting the theory a la Stueckelberg, and implementing Lorentz-like gauges to the metric perturbations, we confirm that the pure theory propagates one scalar degree of freedom, while the full theory contains two tensor modes in addition. We then consider the degrees of freedom by directly examining the metric perturbations. We show that the degrees of freedom of the full theory match with those obtained with the manifestly covariant approach. In contrast, we find that the pure R2 gravity has no degrees of freedom. We show that a similar discrepancy between the two approaches appears also in a theory dual to the three-form, and appears due to the Lorentz-like gauges, which lead to the fictitious modes even after the residual gauge redundancy has been taken into account. At first sight, this implies a discontinuity between the full theory and the pure case. By studying the first-order corrections of the full R2 gravity beyond the linear regime, we show that at high-energies, both scalar and tensor degrees of freedom become strongly coupled. This implies that the apparent discontinuity of pure and full R2 gravity is just an artefact of the perturbation theory, and further supports the absence of degrees of freedom in the pure R2 gravity.

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Traversable Morris–Thorne–Buchdahl wormholes in quadratic gravity

Cited by 14 publications

References 67 publications

A stationary axisymmetric vacuum solution for pure ² gravity

A stationary axisymmetric vacuum solution for pure ² gravity

Closed Timelike Curves Induced by a Buchdahl-Inspired Vacuum Spacetime in R2 Gravity

On the degrees of freedom of R2 gravity in flat spacetime

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Traversable Morris–Thorne–Buchdahl wormholes in quadratic gravity

Cited by 14 publications

References 67 publications

A stationary axisymmetric vacuum solution for pure 2 gravity

A stationary axisymmetric vacuum solution for pure 2 gravity

Closed Timelike Curves Induced by a Buchdahl-Inspired Vacuum Spacetime in R2 Gravity

On the degrees of freedom of R2 gravity in flat spacetime

Contact Info

Product

Resources

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A stationary axisymmetric vacuum solution for pure ² gravity

A stationary axisymmetric vacuum solution for pure ² gravity