Generic slow-roll and non-gaussianity parameters in <i>f</i>(<i>R</i>) theories

Miranda, Tays; Escamilla-Rivera, Celia; Piattella, Oliver F.; Fabris, J. C.

doi:10.1088/1475-7516/2019/05/028

Cited by 24 publications

(15 citation statements)

References 24 publications

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“…In the frame of f (R) gravity the dynamical behavior of the matter field and dark energy has been studied [41][42][43][44]. From the viewpoint of cosmology, many researchers have been carried out their studies from different directions [45][46][47][48][49][50][51][52][53][54][55][56][57][58]. A spherically symmetric vacuum BH solution in f (R) gravity has been derived in [59][60][61][62].…”

Section: Introductionmentioning

confidence: 99%

Nontrivial black hole solutions inf(R)gravitational theory

Nashed

Nojiri

2020

Phys. Rev. D

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Recent observation shows that general relativity (GR) is not valid in the strong regime. f (R) gravity where R is the Ricci scalar, is regarded to be one of good candidates able to cure the anomalies appeared in the conventional general relativity. In this realm, we apply the equation of motions of f (R) gravity to a spherically symmetric spacetime with two unknown functions and derive original black hole (BH) solutions without any constrains on the Ricci scalar as well as on the form of f (R) gravity. Those solutions depend on a convolution function and are deviating from the Schwarzschild solution of the Einstein GR. These solutions are characterized by the gravitational mass of the system and the convolution function that in the asymptotic form gives extra terms that are responsible to make such BHs different from GR. Also, we show that these extra terms make the singularities of the invariants much weaker than those of the GR BH. We analyze such BHs using the trend of thermodynamics and show their consistency with the well known quantities in thermodynamics like the Hawking radiation, entropy and quasi-local energy. We also show that our BH solutions satisfy the first law of thermodynamics. Moreover, we study the stability analysis using the odd-type mode and shows that all the derived BHs are stable and have radial speed equal to one. Finally, using the geodesic deviations we derive the stability conditions of these BHs.

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Section: Introductionmentioning

confidence: 99%

Nontrivial black hole solutions inf(R)gravitational theory

Nashed

Nojiri

2020

Phys. Rev. D

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“…Putting the value of Ḟ = ṘF in the equation (44) and using the values of F and F where F = ∂ 2 f /∂R 2 , where prime denotes the derivative w.r.t. R, we have…”

Section: Inflationary Dynamics and Reheating Temperature In The Jorda...mentioning

confidence: 99%

Constraining $f(R)$ model through spectral indices and reheating temperature

Sharma,

Verma

2020

Preprint

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We investigate a form of f (R) = R 1+δ /R δ c and study the viability of the model for inflation in the Jordan and the Einstein frames. This model is further analysed by using the power spectrum indices of the inflation and the reheating temperature. During the inflationary evolution, the model predicts a value of δ parameter very close to one (δ = 0.98), while the reheating temperature Tre ∼ 10 17 GeV at δ = 0.98 is consistent with the standard approach to inflation and observations. We calculate the slow roll parameters for the minimally coupled scalar field within the framework of our model. It is found that the values of the scalar spectral index and tensor-to-scalar ratio are very close to the recent observational data, including those released by Planck 2018. We also show that the Jordan and the Einstein frames are equivalent when δ ∼ 1 by using the scalar spectral index, tensor-to-scalar ratio and reheating temperature.

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“…In the framework of f (R) gravity, the dynamical behavior of matter and curvature fields has been studied in several works. See, for example, [53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70].…”

Section: Introductionmentioning

confidence: 99%

Anisotropic compact stars in f(R) gravity

Nashed

Capozziello

2021

Eur. Phys. J. C

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We derive a new interior solution for stellar compact objects in $$f\mathcal {(R)}$$ f ( R ) gravity assuming a differential relation to constrain the Ricci curvature scalar. To this aim, we consider specific forms for the radial component of the metric and the first derivative of $$f\mathcal {(R)}$$ f ( R ) . After, the time component of the metric potential and the form of $$f({\mathcal {R}})$$ f ( R ) function are derived. From these results, it is possible to obtain the radial and tangential components of pressure and the density. The resulting interior solution represents a physically motivated anisotropic neutron star model. It is possible to match it with a boundary exterior solution. From this matching, the components of metric potentials can be rewritten in terms of a compactness parameter C which has to be $$C=2GM/Rc^2<<0.5$$ C = 2 G M / R c 2 < < 0.5 for physical consistency. Other physical conditions for real stellar objects are taken into account according to the solution. We show that the model accurately bypasses conditions like the finiteness of radial and tangential pressures, and energy density at the center of the star, the positivity of these components through the stellar structure, and the negativity of the gradients. These conditions are satisfied if the energy-conditions hold. Moreover, we study the stability of the model by showing that Tolman–Oppenheimer–Volkoff equation is at hydrostatic equilibrium. The solution is matched with observational data of millisecond pulsars with a withe dwarf companion and pulsars presenting thermonuclear bursts.

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Generic slow-roll and non-gaussianity parameters in f(R) theories

Cited by 24 publications

References 24 publications

Nontrivial black hole solutions inf(R)gravitational theory

Nontrivial black hole solutions inf(R)gravitational theory

Constraining $f(R)$ model through spectral indices and reheating temperature

Anisotropic compact stars in f(R) gravity

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