Unveiling the Dynamics of the Universe

Avelino, P. P.; Barreiro, Tiago; Carvalho, C. S.; Silva, Antônio da; Martín–Moruno, Prado; Mimoso, José P.; Nunes, Nelson J.; Rubiera-García, Diego; Sáez-Gómez, Diego; Sousa, L.; Tereno, I.; Trindade, A. M. M.

doi:10.3390/sym8080070

Cited by 50 publications

(29 citation statements)

References 382 publications

(582 reference statements)

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“…where f (φ), g(φ) and λ(φ) are arbitrary functions of the scalar field φ. A comparison with the action (26) of the HMPG theory in the scalar-tensor representation shows that its action is indedd of Bergmann-Wagoner-…”

Section: Scalar-tensor Formulationmentioning

confidence: 99%

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Spherically symmetric static vacuum solutions in hybrid metric-Palatini gravity

et al. 2019

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We consider vacuum static spherically symmetric solutions in the hybrid metric-Palatini gravity theory, which is a combination of the metric and Palatini f (R) formalisms unifying local constraints at the Solar System level and the late-time cosmic acceleration. We adopt the scalar-tensor representation of the hybrid metric-Palatini theory, in which the scalar-tensor definition of the potential can be represented as a Clairaut differential equation. Due to their mathematical complexity, it is difficult to find exact solutions of the vacuum field equations, and therefore we adopt a numerical approach in studying the behavior of the metric functions and of the scalar field. After reformulating the field equations in a dimensionless form, and by introducing a suitable independent radial coordinate, the field equations are solved numerically. We detect the formation of a black hole from the presence of Killing horizon for the time-like Killing vector in the metric tensor components. Several models, corresponding to different functional forms of the scalar field potential are considered. The thermodynamic properties of these black hole solutions (horizon temperature, specific heat, entropy and evaporation time due to Hawking luminosity) are also investigated in detail.

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Section: Scalar-tensor Formulationmentioning

confidence: 99%

“…In a more general approach one modifies both the geometric and the matter terms in the Hilbert-Einstein action, thus allowing a coupling between matter and geometry [16,17]. For reviews and in depth discussions of f (R) and other modified gravity theories see [18][19][20][21][22][23][24][25][26][27].…”

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confidence: 99%

Spherically symmetric static vacuum solutions in hybrid metric-Palatini gravity

et al. 2019

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“…As corollary, Lovelock's theorem [18,19] implies any infrared departure from GR must bring in new degrees of freedom (DoFs). Usually one refers to these proposals as modified gravity (MG) theories [5,20,21,22,23,24,25,26,27,28,29,30]. The simplest modification is to introduce an extra scalar DoF to GR thereby accessing the realm of scalar-tensor theories [31,32,33,24,25,34,5,26,35,29].…”

Section: Introductionmentioning

confidence: 99%

Effective field theory of dark energy: A review

2020

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The discovery of cosmic acceleration has triggered a consistent body of theoretical work aimed at modeling its phenomenology and understanding its fundamental physical nature. In recent years, a powerful formalism that accomplishes both these goals has been developed, the so-called effective field theory of dark energy. It can capture the behavior of a wide class of modified gravity theories and classify them according to the imprints they leave on the smooth background expansion history of the Universe and on the evolution of linear perturbations. The effective field theory of dark energy is based on a Lagrangian description of cosmological perturbations which depends on a number of functions of time, some of which are non-minimal couplings representing genuine deviations from standard gravity. Such a formalism is thus particularly convenient to fit and interpret the wealth of new data that will be provided by future galaxy surveys. Despite its recent appearance, this formalism has already allowed a systematic investigation of what lies beyond the standard gravity landscape and provided a conspicuous amount of theoretical predictions and observational results. In this review, we report on these achievements. Conclusion and outlook 94Appendix A Acronyms and symbols 971. Scalar-tensor theoriesà la Brans-Dicke, hereafter dubbed Generalized

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“…They are also employed as phenomenological tools to address issues like singularities, early cosmology, astrophysics, and alternatives to the dark matter/energy paradigm [see e.g. [135–138] for some reviews].…”

Section: Wormholes In Born–infeld and Quadratic Palatini Gravitymentioning

confidence: 99%

Palatini wormholes and energy conditions from the prism of general relativity

2017

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Wormholes are hypothetical shortcuts in spacetime that in general relativity unavoidably violate all of the pointwise energy conditions. In this paper, we consider several wormhole spacetimes that, as opposed to the standard designer procedure frequently employed in the literature, arise directly from gravitational actions including additional terms resulting from contractions of the Ricci tensor with the metric, and which are formulated assuming independence between metric and connection (Palatini approach). We reinterpret such wormhole solutions under the prism of General Relativity and study the matter sources that thread them. We discuss the size of violation of the energy conditions in different cases and how this is related to the same spacetimes when viewed from the modified gravity side.

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Unveiling the Dynamics of the Universe

Cited by 50 publications

References 382 publications

Spherically symmetric static vacuum solutions in hybrid metric-Palatini gravity

Spherically symmetric static vacuum solutions in hybrid metric-Palatini gravity

Effective field theory of dark energy: A review

Palatini wormholes and energy conditions from the prism of general relativity

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