Modified Gr and Helium Nucleosynthesis

Al-Rawaf, A. S.

doi:10.1142/s021827180500753x

Cited by 25 publications

(16 citation statements)

References 15 publications

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“…In fact, Rastall theory of gravity presents various good behaviors. It seems consistent with the Universe age and with the Hubble parameter [30], with the helium nucleosynthesis [31] and with the gravitational lensing phenomena [32]. It permits an alternative description for the matter dominated era with respect to general relativity [33].…”

Section: B Rastall Theorysupporting

confidence: 68%

4-Index theory of gravity and its relation with the violation of the energy–momentum conservation law

et al. 2019

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Recently, a 4-index generalization of the Einstein theory is proposed by Moulin [1]. Using this method, we find the most general 2-index field equations derivable from the Einstein-Hilbert action. The application of Newtonian limit, the role of gravitational coupling constant and the effects of the properties of ordinary energy-momentum tensor in obtaining a 4-index gravity theory have been studied. We also address the results of building Weyl free 4-index gravity theory. Our study displays that both the Einstein and Rastall theories can be obtained as the subclasses of a 4-index gravity theory which shows the power of 4-index method in unifying various gravitational theories. It is also obtained that the violation of the energy-momentum conservation law may be allowed in 4-index gravity theory, and moreover, the contraction of 4-index theory generally admits a non-minimal coupling between geometry and matter field in the Rastall way. This study also shows that, unlike the Einstein case, the gravitational coupling constant of 4-index Rastall theory generally differs from that of the ordinary 2-index Rastall theory.

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Section: B Rastall Theorysupporting

confidence: 68%

4-Index theory of gravity and its relation with the violation of the energy–momentum conservation law

et al. 2019

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“…OCL, as one of the cornerstones of GR [34], is not respected in all modified gravity theories, for example, it is broken in the non-minimal curvature matter coupling theories [35][36][37][38][39][40][41][42][43][44]. Rastall gravity is a pioneering theory in this area [42] in accordance with various observations [45][46][47][48][49][50][51][52][53][54][55][56][57] and its corresponding cosmology avoids the age and entropy problems arisen in the framework of the standard cosmology [58]. In fact, this theory can even provide a better platform for describing the matter dominated era compared to the Einstein theory [47].…”

Section: Introductionmentioning

confidence: 78%

Non-minimal coupling inspires the Dirac cosmological model

Moradpour,

Shabani,

Ziaie

et al. 2021

Preprint

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In the framework of the generalized Rastall theory (GRT), we study the ability of a non-minimal coupling between geometry and matter fields in order to provide a setting which allows for a variable G during the cosmic evolution. In this regard, the compatibility of this theory with Dirac hypothesis on the variations of G is investigated, and additionally, the possibility of obtaining the current accelerated universe is also addressed. In summary, our study indicates that, in GRT, having in hand the G profile, one may find the corresponding non-minimal coupling between the energy source and geometry and vise versa, in a compatible way with the current accelerated universe.

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“…Moreover, Rastall gravity can provide an alternative description for matter dominated era in comparison with GR [17]. It is also supported by observational data from the helium nucleosynthesis [18]. Also, motivated by these evidences, physicists have tried to investigate various cosmic epochs in this framework [19] and in [20], it is argued that this theory does not suffer from the entropy and age problems that appear in the context of standard cosmology.…”

Section: Introductionmentioning

confidence: 84%

Structure Formation in Generalized Rastall Gravity

Ziaie,

Moradpour,

Shabani

2020

Preprint

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Recently a modified version of Rastall gravity has been proposed in which a varying coupling parameter could play the role of dark energy (DE) and thus is responsible for the current accelerated expansion of the Universe. Motivated by this modification, we study here the evolution of matter perturbations, in both linear and non-linear regimes, using the top-hat spherical collapse model. The exact solutions in linear regime show that as the Universe evolves, matter perturbations grow and reach a maximum value at a certain redshift after which the perturbations start decreasing at later times. Depending on model parameters, exact oscillatory solutions (in linear regime) can be found representing that matter perturbations could experience either overdense and underdense regions during the dynamical evolution of the Universe. Numerical solutions in non-linear regime show that the amplitude of perturbations grow much faster than the linear one and diverges at a critical redshift. The growth rate of non-linear perturbations and the critical redshift depend crucially on model parameters. It is found that the running mutual interaction between matter and geometry, encoded in the variable Rastall coupling parameter, could affect on the dynamics of matter perturbations during the evolution of the Universe.

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Modified Gr and Helium Nucleosynthesis

Cited by 25 publications

References 15 publications

4-Index theory of gravity and its relation with the violation of the energy–momentum conservation law

4-Index theory of gravity and its relation with the violation of the energy–momentum conservation law

Non-minimal coupling inspires the Dirac cosmological model

Structure Formation in Generalized Rastall Gravity

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