Stealth black holes in shift symmetric kinetic gravity braiding

Bernardo, Reginald Christian; Celestial, John de Leon; Vega, Ian

doi:10.1103/physrevd.101.024036

Cited by 16 publications

(11 citation statements)

References 135 publications

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“…(3.68). We note that the unhealthy de Sitter state given covariantly by A X = 0 or at component level by the equation 3H 2 = ρ Λ can be identified as a stealth solution wherein the background field equations reduce merely to that of GR [28]. The ghost can then be traced to the same one surrounding stealth black holes and can be alleviated using the scordatura mechanism [52][53][54].…”

Section: Ghost and Laplace Stability Conditionsmentioning

confidence: 94%

“…Recent results even show that the Galileon ghost condensate [25] and the generalized cubic covariant Galileon [26] theories of the tadpole-free shift symmetric sector of KGB can be as compatible with cosmological observations as the ΛCDM model. Interestingly, the same sector also houses hairy black holes and could be potentially rich with observational signatures from the strong gravity regime [27][28][29].…”

Section: Introductionmentioning

confidence: 99%

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Self-tuning kinetic gravity braiding: Cosmological dynamics, shift symmetry, and the tadpole

Bernardo

2021

Preprint

Self Cite

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We study the self-tuning subclass of kinetic gravity braiding and obtain robust predictions on self-tuning and dynamics in the tadpole-free shift symmetric sector of the theory. In particular, we show inevitability of cosmic acceleration, prove the dynamical stability of this late-time asymptotic state, and derive ghost and gradient stability constraints on the self-tuning vacuum. We discuss the results concretely in the context of generalized cubic covariant Galileon theory and an exponential kinetic gravity braiding.

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Section: Ghost and Laplace Stability Conditionsmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Self-tuning kinetic gravity braiding: Cosmological dynamics, shift symmetry, and the tadpole

Bernardo

2021

Preprint

Self Cite

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“…There, we dubbed these closed form solutions as effectively vacuum confiurations. Another interesting analogy is provided by the 'stealth' BH solutions in various alternative models of gravity (see e.g., [18,19] and references therein). Such configurations feature a nontrivial scalar field, while the geometry is still that of the (vacuum) general relativity solutions)).…”

Section: The D = 3 Casementioning

confidence: 99%

“…in the Lagrangians ( 14)- (16). With this choice, setting φ = φ a = 0 results in (pure gravity) CS Lagrangian in d = 2n + 1 dimensions, with a negative cosmological constant Λ.…”

Section: The General Csg Lagrangians and The Connection With The Einstein-lovelock Hierarchymentioning

confidence: 99%

Higgs–Chern–Simons Gravity Models in d = 2n + 1 Dimensions

Radu

Tchrakian

2020

Symmetry

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We consider a family of new Higgs–Chern–Simons (HCS) gravity models in 2n+1 dimensions (n=1,2,3). This provides a generalization of the (usual) gravitational Chern–Simons (CS) gravities resulting from non-Abelian CS densities in all odd dimensions, which feature vector and scalar fields, in addition to the metric. The derivation of the new HCS gravitational (HCSG) actions follows the same method as in the usual-CSG case resulting from the usual CS densities. The HCSG result from the HCS densities, which result through a one-step descent of the Higgs–Chern–Pontryagin (HCP), with the latter being descended from Chern-Pontryagin (CP) densities in some even dimension. A preliminary study of the solutions of these models is considered, with exact solutions being reported for spacetime dimensions d=3,5.

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“…For a stealth de Sitter solution in DHOST theories see [39], and for stealth black hole solutions in scalar-tensor theories see Refs. [34,36,[40][41][42][43][44][45][46][47][47][48][49][50], among which the most general case, the Kerr-Newman-de Sitter solution in the DHOST theories, was obtained in [36]. The difference between the standard GR solutions and stealth solutions in scalar-tensor theories arises at the level of perturbations due to the scalar field perturbations.…”

Section: Introductionmentioning

confidence: 99%

Stealth dark energy in scordatura DHOST theory

Gorji,

Motohashi,

Mukohyama

2020

Preprint

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A stealth de Sitter solution in scalar-tensor theories has an exact de Sitter background metric and a nontrivial scalar field profile. Recently, in the context of Degenerate Higher Order Scalar Tensor (DHOST) theories it was shown that stealth de Sitter solutions suffer from either infinite strong coupling or gradient instability for scalar field perturbations. The sound speed squared is either vanishing or negative, for the former of which the strong coupling scale is zero and thus lower than the energy scale of any physical phenomena. From the viewpoint of effective field theory, this issue is naturally resolved by introducing a controlled detuning of the degeneracy condition dubbed scordatura, recovering a version of ghost condensation. In this paper we construct a viable dark energy model in the scordatura DHOST theory based on a stealth cosmological solution, in which the metric is the same as in the standard ΛCDM model and the scalar field profile is linearly time-dependent. We show that the scordatura mechanism resolves the strong coupling and gradient instability. Further, we find that the scordatura is also necessary to make the quasi-static limit well-defined, which implies that the subhorizon observables are inevitably affected by the scordatura. We derive the effective gravitational coupling and the correction to the friction term for the subhorizon evolution of the linear dark matter energy density contrast as well as the Weyl potential and the gravitational slip parameter. In the absence of the scordatura, the quasi-static approximation would breakdown at all scales around stealth cosmological solutions even if the issue of the infinite strong coupling is unjustly disregarded. Therefore previous estimations of the subhorizon evolution of matter density contrast in modified gravity in the literature need to be revisited by taking into account the scordatura effect.

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Stealth black holes in shift symmetric kinetic gravity braiding

Cited by 16 publications

References 135 publications

Self-tuning kinetic gravity braiding: Cosmological dynamics, shift symmetry, and the tadpole

Self-tuning kinetic gravity braiding: Cosmological dynamics, shift symmetry, and the tadpole

Higgs–Chern–Simons Gravity Models in d = 2n + 1 Dimensions

Stealth dark energy in scordatura DHOST theory

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