General theory of cosmological perturbations in open and closed universes from the Horndeski action

Akama, Shingo; Kobayashi, Tsutomu

doi:10.1103/physrevd.99.043522

Cited by 24 publications

(18 citation statements)

References 79 publications

(99 reference statements)

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“…For ξ = O(1) we have γ − 1 = O(1), which clearly contradicts the solar-system experiments [221]. Now we add a Galileon-like cubic interaction to (134):…”

Section: A Vainshtein Primermentioning

confidence: 79%

Horndeski theory and beyond: a review

2019

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This article is intended to review the recent developments in the Horndeski theory and its generalization, which provide us with a systematic understanding of scalar-tensor theories of gravity as well as a powerful tool to explore astrophysics and cosmology beyond general relativity. This review covers the generalized Galileons, (the rediscovery of) the Horndeski theory, cosmological perturbations in the Horndeski theory, cosmology with a violation of the null energy condition, degenerate higher-order scalar-tensor theories and their status after GW170817, the Vainshtein screening mechanism in the Horndeski theory and beyond, and hairy black hole solutions.

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“…For ξ = O(1) we have γ − 1 = O(1), which clearly contradicts the solar-system experiments [221]. Now we add a Galileon-like cubic interaction to (134):…”

Section: A Vainshtein Primermentioning

confidence: 79%

Horndeski theory and beyond: a review

2019

Self Cite

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“…Recently, striking studies have been conducted. A quite wide class of singularity-free cosmological solutions in Friedmann-Lemaître-Robertson-Walker (FLRW) spacetime is proved to be unstable [16][17][18][19]. Since the no-go theorem is established based on the Horndeski theory, in other words, the most generalized scalartensor theory whose equation of motion is up to second order [20], one may consider it is difficult to find stable cosmological solutions without a singularity.…”

Section: Introductionmentioning

confidence: 99%

Stable singularity-free cosmological solutions in nonprojectable Hořava-Lifshitz gravity

et al. 2019

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We find stable singularity-free cosmological solutions in non-flat Friedmann-Lemaître-Robertson-Walker (FLRW) spacetime in the context of Hořava-Lifshitz (HL) theory. Although we encounter the negative squared effective masses of the scalar perturbations in the original HL theory, the behaviors can be remedied by relaxing the projectability condition. In our analysis, the effects from the background dynamics are taken into account as well as the sign of the coefficients in the quadratic action for perturbations. More specifically, we give further classification of the gradient stability/instability into five types. These types are defined in terms of the effective squared masses of perturbations M 2 , the effective friction coefficients in perturbation equations H and these magnitude relations |M 2 |/H 2 . Furthermore, we indicate that oscillating solutions possibly show a kind of resonance especially in open FLRW spacetime. We find that the higher order spatial curvature terms with Lifshitz scaling z = 3 are significant to suppress the instabilities due to the background dynamics.PACS numbers: 98.80.Cq

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“…Not only the time crystal Universe but any bouncing Universe in Horndeski theory tends to suffer from the stability issue [27]. In case of the Universe with a spatial curvature, the stability is studied [28] and found that the tensor perturbation is stable if and only if the following inequalities are satisfied:…”

Section: Summary and Discussionmentioning

confidence: 99%

“…These analyses show the presence of gradient instability [25,26] and finally no-go theorem for stable bouncing cosmology in Horndeski theory was found for the spatially flat Universe [27]. However, it was shown that no-go theorem does not hold when the spatial curvature is included [28]. Therefore, we should consider Horndeski theory in the presence of a spatial curvature in order to have a bouncing Universe [29].…”

Section: Introductionmentioning

confidence: 96%

Birth of de Sitter universe from a time crystal universe

Yoshida

Soda

2019

Phys. Rev. D

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We show that a simple sub-class of Horndeski theory can describe a time crystal Universe. The time crystal Universe can be regarded as a baby Universe nucleated from a flat space, which is mediated by an extension of Giddings-Strominger instanton in a 2-form theory dual to the Horndeski theory. Remarkably, when a cosmological constant is included, de Sitter Universe can be created by tunneling from the time crystal Universe. It gives rise to a past completion of an inflationary Universe. *

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General theory of cosmological perturbations in open and closed universes from the Horndeski action

Cited by 24 publications

References 79 publications

Horndeski theory and beyond: a review

Horndeski theory and beyond: a review

Stable singularity-free cosmological solutions in nonprojectable Hořava-Lifshitz gravity

Birth of de Sitter universe from a time crystal universe

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