Scalar-Tensor Gravity

Faraoni, Valerio

doi:10.1007/978-1-4020-1989-0_1

Cited by 331 publications

(692 citation statements)

References 14 publications

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“…These expressions for f, R, H fulfill equation (9). The system has also a constant of motion µ 0 = 0 given by equation (48), as the Lagrangian possesses a Noether symmetry.…”

Section: Radiation Solutionsmentioning

confidence: 93%

f(R) cosmology from Noether’s symmetry

Capozziello

Felice

2008

J. Cosmol. Astropart. Phys.

198

214

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A general approach to find out exact cosmological solutions in f (R)-gravity is discussed. Instead of taking into account phenomenological models, we assume, as a physical criterium, the existence of Noether symmetries in the cosmological f (R) Lagrangian. As a result, the presence of such symmetries selects viable models and allow to solve the equations of motion. We discuss also the case in which no Noether charge is present but general criteria can be used to achieve solutions.PACS numbers: 04.50.+h, 95.36.+x, 98.80.-k

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“…These expressions for f, R, H fulfill equation (9). The system has also a constant of motion µ 0 = 0 given by equation (48), as the Lagrangian possesses a Noether symmetry.…”

Section: Radiation Solutionsmentioning

confidence: 93%

f(R) cosmology from Noether’s symmetry

Capozziello

Felice

2008

J. Cosmol. Astropart. Phys.

198

214

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“…This condition does not necessarily satisfy. This is the reason that usually the authors keep ω in the literatures (See [12] transformed to a new action in which a newfor different suggestions of function ω).…”

Section: Scalar Perturbations In Generalized Scalar-tensor Gravitymentioning

confidence: 99%

“…Here we are interested in deriving the initial conditions of modified Mukhanov-Sasaki equation in generalized scalar tensor gravity, described by the Lagrangian density √ −g f (R, φ) [11][12][13][14]. This is one of the most general modification of general relativity and includes the higher order terms of the scalar curvature, R and also a scalar field φ as a dynamical degree of freedom in addition to the usual metric tensor g μν .…”

Section: Introductionmentioning

confidence: 99%

On the initial conditions of scalar and tensor fluctuations in $$f(R,\phi )$$ f ( R , ϕ ) gravity

Cheraghchi

Shojai

2018

Eur. Phys. J. C

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We have considered the perturbation equations governing the growth of fluctuations during inflation in generalized scalar tensor theory f (R, φ). We have found that the scalar metric perturbations at very early times are negligible compared to the scalar field perturbation, just like general relativity. At sufficiently early times, when the physical momentum of perturbation mode, q/a is much larger than the Hubble parameter H , i.e. q/a H , we have obtained the metric and scalar field perturbation in the form of WKB solutions up to an undetermined coefficient. Then we have quantized the scalar fluctuations and expanded the metric and the scalar field perturbations with the help of annihilation and creation operators of the scalar field perturbation. The standard commutation relations of annihilation and creation operators fix the unknown coefficient. Going over to the gauge invariant quantities which are conserved beyond the horizon, we have obtained the initial condition of the generalized Mukhanov-Sasaki equation. Then a similar procedure is performed for the case of tensor metric perturbation. As an example of the generalized Mukhanov-Sasaki equation and its initial condition, we have proposed a power-law functional form as f (R, φ) = f 0 R m φ n and obtained an exact inflationary solution. In this background, then we have discussed how the scalar and tensor fluctuations grow.

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“…theory endowed with a cosmological constant. For scalar-tensor theories, consult the books by Berman (2007), Faraoni (2004), and Fujii and Maeda (2003). In Berman (2007a), we find a rationale for the existence of a cosmological "constant", though we must remember that a negative cosmic pressure may be also responsabilized for accelerated expansion, which includes exponential inflation.…”

Section: Introductionmentioning

confidence: 99%

Inflationary Phase in a Generalized Brans-Dicke Theory

Berman¹,

Trevisan²

2009

Int J Theor Phys

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We find a solution for exponential inflation in a Brans-Dicke generalized model, where the coupling "constant " is variable. While in General Relativity the equation of state is p = −ρ, here we find p = αρ, where α < −2/3. The negativity of cosmic pressure implies acceleration of the expansion, even with Λ < 0 . PACS 98.80 Hw 1 INFLATIONARY PHASE IN A GENERALIZED BRANS-DICKE THEORYInternational Journal of Theoretical Physics, to be published.

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Scalar-Tensor Gravity

Abstract: The analysis of certain singularities in scalar-tensor gravity contained in a recent paper is completed, and situations are pointed out in which these singularities cannot occur.

Cited by 331 publications

References 14 publications

f(R) cosmology from Noether’s symmetry

f(R) cosmology from Noether’s symmetry

On the initial conditions of scalar and tensor fluctuations in $$f(R,\phi )$$ f ( R , ϕ ) gravity

Inflationary Phase in a Generalized Brans-Dicke Theory

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