Rastall Cosmology

Fabris, J. C.; Piattella, Oliver F.; Rodrigues, Davi C.; Batista, C.E.M.; Daouda, M. Hamani

doi:10.1142/s2010194512008227

Cited by 70 publications

(47 citation statements)

References 19 publications

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“…Therefore, because λ is constant and the R(4κ λ − 1) = κ T condition applies to all spacetimes and energy-momentum sources, the κ λ = 1 4 case is not allowed [23]. More studies on the various aspects of this theory can be found in [74,[77][78][79][80][81][82][83][84][85][86][87][88][89][90].…”

Section: A Brief Review On the Rastall Theorymentioning

confidence: 99%

A generalization to the Rastall theory and cosmic eras

Moradpour¹,

Heydarzade²,

Darabi³

et al. 2017

Eur. Phys. J. C

127

142

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A generalized version for the Rastall theory is proposed showing the agreement with the cosmic accelerating expansion. In this regard, a coupling between geometry and the pressureless matter fields is derived which may play the role of dark energy, responsible for the current accelerating expansion phase. Moreover, our study also shows that the radiation field may not be coupled to the geometry in a non-minimal way which represents that the ordinary energymomentum conservation law is respected by the radiation source. It is also shown that the primary inflationary era may be justified by the ability of the geometry to couple to the energy-momentum source in an empty flat FRW universe. In fact, this ability is independent of the existence of the energymomentum source and may compel the empty flat FRW universe to expand exponentially. Finally, we consider a flat FRW universe field by a spatially homogeneous scalar field evolving in potential V(φ), and study the results of applying the slow-roll approximation to the system which may lead to an inflationary phase for the universe expansion.

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Section: A Brief Review On the Rastall Theorymentioning

confidence: 99%

A generalization to the Rastall theory and cosmic eras

Moradpour¹,

Heydarzade²,

Darabi³

et al. 2017

Eur. Phys. J. C

127

142

View full text Add to dashboard Cite

show abstract

“…Observational data from the helium nucleosynthesis seem also in agreement with Rastall gravity [17]. Based on these observational evidences, there have been some recently studies of the various cosmic eras in the framework of Rastall gravity [18][19][20][21][22]. Other interesting a e-mail: cordac.galilei@gmail.com issues are that Rastall gravity seems to do not suffer from the entropy and age problems of standard cosmology [23] and is consistent with the gravitational lensing phenomena [24,25].…”

mentioning

confidence: 90%

Einstein and Rastall theories of gravitation in comparison

Darabi

Moradpour

Licata³

et al. 2018

Eur. Phys. J. C

168

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We profit by a recent paper of Visser claiming that Rastall gravity is equivalent to Einstein gravity to compare the two gravitational theories in a general way. Our conclusions are different from Visser's ones. We indeed argue that these two theories are not equivalent. In fact, Rastall theory of gravity is an "open" theory when compared to Einstein general theory of relativity. Thus, it is ready to accept the challenges of observational cosmology and quantum gravity.The framework of extended theories of gravity [1][2][3][4][5] is today considered an useful and popular approach to attempt to solve the important problems of the standard model of cosmology like Dark Energy [6,7] and Dark Matter [8,9]. A key point is that all of the potential alternatives to Einstein's general theory of relativity (GTR) must be viable. This implies that alternative theories must be in agreement with the Einstein's equivalence principle, which has today a strong, unchallengeable empirical evidence [2]. The fundamental consequence is that the alternatives to Einstein gravity must be metric theories [2]. Another important point is that such alternatives must pass the solar system tests. Hence, deviations from the standard GTR must be weak [1,2].Within the framework of extended gravity, one finds the theory proposed by Rastall in 1972 [10], which recently obtained a renewed interest in the literature [11][12][13][14]. This interest is due to some good behavior of the Rastall theory. In fact, on one hand it seems in good agreement with observational data on the Universe age and on the Hubble parameter [15]. On the other hand it may, in principle, provide an alternative description for the matter dominated era with respect to the GTR [16]. Observational data from the helium nucleosynthesis seem also in agreement with Rastall gravity [17]. Based on these observational evidences, there have been some recently studies of the various cosmic eras in the framework of Rastall gravity [18][19][20][21][22]. Other interesting a e-mail: cordac.galilei@gmail.com issues are that Rastall gravity seems to do not suffer from the entropy and age problems of standard cosmology [23] and is consistent with the gravitational lensing phenomena [24,25]. Further interesting works on Rastall gravity are given by [26][27][28][29][30] and references within.Differently from Einstein gravity, Rastall gravity considers a non-divergence-free energy-momentum . A different, but similar theory is the so called Curvature-matter theory of gravity [31][32][33][34][35]. In this theory the matter and geometry are coupled to each other in a non-minimal way [31][32][33][34][35]. Then, the standard energy-momentum conservation law does not work in this case too [31][32][33][34][35].In a recent paper [36], Visser claimed that Rastall gravity is equivalent to Einstein gravity. In this letter, we argue that these two theories are not equivalent instead. Let us see the key points of our interpretation.Rastall did not define a new energy-momentum tensor (EMT) in his origina...

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“…In this way, Rastall's theory may be viewed as a classical, phenomenological way to implement some concepts that are typical of a quantum theory of gravity. While Rastall's theory has already been studied in the context of the present evolution of the universe [6][7][8][9][10], its application to the primordial universe is still lacking.…”

Section: Introductionmentioning

confidence: 99%

Bouncing solutions in Rastall’s theory with a barotropic fluid

et al. 2013

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Rastall's theory is a modification of Einstein's theory of gravity where the covariant divergence of the stress-energy tensor is no more vanishing, but proportional to the gradient of the Ricci scalar. The motivation of this theory is to investigate a possible non-minimal coupling of the matter fields to geometry which, being proportional to the curvature scalar, may represent an effective description of quantum gravity effects. Non-conservation of the stressenergy tensor, via Bianchi identities, implies new field equations which have been recently used in a cosmological context, leading to some interesting results. In this paper we adopt Rastall's theory to reproduce some features of the effective Friedmann's equation emerging from loop quantum cosmology. We determine a class of bouncing cosmological solutions and comment about the possibility of employing these models as effective descriptions of the full quantum theory. *

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Rastall Cosmology

Cited by 70 publications

References 19 publications

A generalization to the Rastall theory and cosmic eras

A generalization to the Rastall theory and cosmic eras

Einstein and Rastall theories of gravitation in comparison

Bouncing solutions in Rastall’s theory with a barotropic fluid

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