Fab Four: When John and George Play Gravitation and Cosmology

Bruneton, Jean-Philippe; Rinaldi, Massimiliano; Kanfon, A. D.; Hees, A.; Schlogel, Sandrine; Füzfa, André

doi:10.1155/2012/430694

Cited by 53 publications

(42 citation statements)

References 38 publications

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“…However, in order for such a theory to be observationally viable, it must employ the Vainshtein mechanism within the solar system to evade fifth force constrains, and recently it has been argued that the need for solar system screening and weak-coupling constrain the cosmological impact of the Fab Four [796]. 51 For related work on the cosmology of this theory, see [793][794][795].…”

Section: Horndeski Theorymentioning

confidence: 99%

Beyond the cosmological standard model

et al. 2015

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After a decade and a half of research motivated by the accelerating universe, theory and experiment have a reached a certain level of maturity. The development of theoretical models beyond Λ or smooth dark energy, often called modified gravity, has led to broader insights into a path forward, and a host of observational and experimental tests have been developed. In this review we present the current state of the field and describe a framework for anticipating developments in the next decade. We identify the guiding principles for rigorous and consistent modifications of the standard model, and discuss the prospects for empirical tests.We begin by reviewing recent attempts to consistently modify Einstein gravity in the infrared, focusing on the notion that additional degrees of freedom introduced by the modification must "screen" themselves from local tests of gravity. We categorize screening mechanisms into three broad classes: mechanisms which become active in regions of high Newtonian potential, those in which first derivatives of the field become important, and those for which second derivatives of the field are important. Examples of the first class, such as f (R) gravity, employ the familiar chameleon or symmetron mechanisms, whereas examples of the last class are galileon and massive gravity theories, employing the Vainshtein mechanism. In each case, we describe the theories as effective theories and discuss prospects for completion in a more fundamental theory. We describe experimental tests of each class of theories, summarizing laboratory and solar system tests and describing in some detail astrophysical and cosmological tests. Finally, we discuss prospects for future tests which will be sensitive to different signatures of new physics in the gravitational sector.The review is structured so that those parts that are more relevant to theorists vs. observers/experimentalists are clearly indicated, in the hope that this will serve as a useful reference for both audiences, as well as helping those interested in bridging the gap between them.

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Section: Horndeski Theorymentioning

confidence: 99%

Beyond the cosmological standard model

et al. 2015

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“…Accelerating behaviors were observed as well in the case of a coupling given by the Ricci tensor [9]. Many models appeared in this context [10][11] [12].…”

Section: Introductionmentioning

confidence: 94%

Asymptotically locally AdS and flat black holes in the presence of an electric field in the Horndeski scenario

2014

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Asymptotically locally AdS and asymptotically flat black hole solutions are found for a particular case of the Horndeski action. The action contains the Einstein-Hilbert term with a cosmological constant, a real scalar field with a non minimal kinetic coupling given by the Einstein tensor, the minimal kinetic coupling and the Maxwell term. There is no scalar potential. The solution has two integration constants related with the mass and the electric charge. The solution is given for all dimensions. A new class of asymptotically locally flat spherically symmetric black holes is found when the minimal kinetic coupling vanishes and the cosmological constant is present. In this case we get a solution which represents an electric Universe. The electric field at infinity is only supported by Λ. When the cosmological constant vanishes the black hole is asymptotically flat.

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“…The nonminimal derivative coupling leads to cosmological models with rich phenomenology, such as solutions containing a Big Bang, expanding Universes with no beginning, cosmological bounces, eternally contracting Universes, a Big Crunch, and a Big Rip avoidance [33,[36][37][38][39][40][41][42]. In particular, it was shown that one is able to explain in a unique manner both a quasi-de Sitter phase and an exit from it without any fine-tuned potential [32].…”

Section: Introductionmentioning

confidence: 99%

Cosmological models in modified gravity theories with extended nonminimal derivative couplings

2017

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We construct gravitational modifications that go beyond Horndeski, namely theories with extended nonminimal derivative couplings, in which the coefficient functions depend not only on the scalar field but also on its kinetic energy. Such theories prove to be ghost-free in a cosmological background. We investigate the early-time cosmology and show that a de Sitter inflationary phase can be realized as a pure result of the novel gravitational couplings. Additionally, we study the latetime evolution, where we obtain an effective dark energy sector which arises from the scalar field and its extended couplings to gravity. We extract various cosmological observables and analyse their behavior at small redshifts for three choices of potentials, namely, for the exponential, the powerlaw, and the Higgs potential. We show that the Universe passes from deceleration to acceleration in the recent cosmological past, while the effective dark-energy equation-of-state parameter tends to the cosmological-constant value at present. Finally, the effective dark energy can be phantom-like, although the scalar field is canonical, which is an advantage of the model.PACS numbers: 04.50. Kd, 95.36.+x

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Fab Four: When John and George Play Gravitation and Cosmology

Cited by 53 publications

References 38 publications

Beyond the cosmological standard model

Beyond the cosmological standard model

Asymptotically locally AdS and flat black holes in the presence of an electric field in the Horndeski scenario

Cosmological models in modified gravity theories with extended nonminimal derivative couplings

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