Nonsingular black holes and nonsingular universes in the regularized Lovelock gravity

Gao, Changjun; Yu, Shuang; Qiu, Jianhui

doi:10.1016/j.dark.2020.100754

Cited by 10 publications

(12 citation statements)

References 66 publications

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“…Such a regularized theory can evade the Lovelock theorem [18], which states that only the metric tensor and Einstein tensor contribute to the dynamics of 4-dimensional spacetime. Besides usual black holes in this theory [16,[19][20][21], regular black holes are also admitted in the Einstein-Lovelock theory [22]. We find that ultracompact objects are as well permitted in such a theory.…”

Section: Introductionmentioning

confidence: 64%

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Strong deflection gravitational lensing by an Einstein–Lovelock ultracompact object

Gao

Xie

2022

Eur. Phys. J. C

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We investigate the strong deflection gravitational lensing by an Einstein–Lovelock ultracompact object. Its unique features are the relativistic images inside its photon sphere which are absent for an Einstein–Lovelock black hole. We obtain its lensing observables and evaluate their observability for the direct images of two supermassive black holes in the Galaxy and M87 respectively, Sgr A* and M87*, and for the relativistic microlensing on a star closely around Sgr A*. We find that although it is impossible to tell difference of the ultracompact object from the black hole in Einstein–Lovelock gravity by the direct images, it might be possible to distinguish the Einstein–Lovelock ultracompact object by measuring the total flux of the relativistic microlensing in the not-so-far future.

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Section: Introductionmentioning

confidence: 64%

“…where the parameter η • with the dimension of [length] 2 has to be introduced to balance the dimension of Eq. ( 6), the explicit form of ψ is, therefore, found as [22]…”

Section: Einstein-lovelock Ultracompact Objectmentioning

confidence: 99%

Strong deflection gravitational lensing by an Einstein–Lovelock ultracompact object

Gao

Xie

2022

Eur. Phys. J. C

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“…We will return to more general solutions, and possible restrictions on solutions in the context of regularised theories below, and for now focus on the behaviours prescribed by Eqs. ( 130)- (131).…”

Section: Background Cosmologymentioning

confidence: 99%

“…In principle, the background evolution, and the evolution of perturbations encoded in Eqs. ( 130)- (131) and Eqs. ( 136)- (138), can be used to constrain 4D Einstein-Gauss-Bonnet, by comparing predictions of the theory against observation, thereby putting constraints on allowed values of α.…”

Section: Constraints On αmentioning

confidence: 99%

The 4D Einstein-Gauss-Bonnet Theory of Gravity: A Review

Fernandes,

Carrilho,

Clifton

et al. 2022

Preprint

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We review the topic of 4D Einstein-Gauss-Bonnet gravity, which has been the subject of considerable interest over the past two years. Our review begins with a general introduction to Lovelock's theorem, and the subject of Gauss-Bonnet terms in the action for gravity. These areas are of fundamental importance for understanding modified theories of gravity, and inform our subsequent discussion of recent attempts to include the effects of a Gauss-Bonnet term in four space-time dimensions by rescaling the appropriate coupling parameter. We discuss the mathematical complexities involved in implementing this idea, and review recent attempts at constructing welldefined, self-consistent theories that enact it. We then move on to consider the gravitational physics that results from these theories, in the context of black holes, cosmology, and weak-field gravity. We show that 4D Einstein-Gauss-Bonnet gravity exhibits a number of interesting phenomena in each of these areas.

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“…Here, we investigate this question within the framework of the so-called regularized 4D Einstein-Lovelock gravity. Recently, a simple dimensional regularization of Lovelock gravity has been discussed in a number of research papers by which the effects of ghost-free, higher-order curvatures can be extended to four-dimensional spacetimes [1,[50][51][52][53][54][55]. As a result of this trick, it is expected that some features of Lovelock gravity may be observed again, or may be lost, or may undergo fundamental changes in four dimensions.…”

mentioning

confidence: 99%

Absence of isolated critical points with nonstandard critical exponents in the four-dimensional regularization of Lovelock gravity

Dehghani,

Setare

2022

Preprint

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Hyperbolic vacuum black holes in Lovelock gravity theories of odd order N are known to have the so-called isolated critical points with nonstandard critical exponents (as α = 0, β = 1, γ = N −1, and δ = N ), different from those of mean-field critical exponents (with α = 0, β = 1/2, γ = 1, and δ = 3). Motivated by this important observation, here, we explore the consequences of taking the D → 4 limit of Lovelock gravity and the possibility of finding nonstandard critical exponents associated with isolated critical points in four-dimensions by use of the four-dimensional regularization, recently proposed by Glavan and Lin [1]. It is shown that the regularized 4D Einstein-Lovelock gravity theories of odd order N > 3 do not possess any physical isolated critical point. In fact, the critical (inflection) points of equation of state always occurs for the branch of black holes with negative entropy. The situation is quite different for the case of the regularized 4D Einstein-Lovelock gravity with cubic curvature corrections (N = 3). In this case (N = 3), although the entropy is nonnegative and the equation of state of hyperbolic vacuum black holes has a nonstandard Taylor expansion about its inflection point, but there is no criticality associated with this special point. At this point, the physical properties of the black hole system change drastically, e.g., both the mass and entropy of the black hole vanishes, meaning that there do not exist degrees of freedom in order for a phase transition to occur. These results are in strong contrast to those findings in Lovelock gravity.

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Nonsingular black holes and nonsingular universes in the regularized Lovelock gravity

Cited by 10 publications

References 66 publications

Strong deflection gravitational lensing by an Einstein–Lovelock ultracompact object

Strong deflection gravitational lensing by an Einstein–Lovelock ultracompact object

The 4D Einstein-Gauss-Bonnet Theory of Gravity: A Review

Absence of isolated critical points with nonstandard critical exponents in the four-dimensional regularization of Lovelock gravity

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