Cosmological inflation driven by a scalar torsion function

Guimarães, T. M.; Lima, RT De; Pereira, S. H.

doi:10.1140/epjc/s10052-021-09076-x

Cited by 18 publications

(10 citation statements)

References 32 publications

(50 reference statements)

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“…Modified gravity theories with curvature-matter coupling [114][115][116] could also be extended to a Finslerian geometric framework. Riemannian geometries with torsion [117,118] or nonmetricity [119][120][121] can also represent a source of inspiration for obtaining their Finslerian analogues.…”

Section: A Metric and Thermodynamic Quantitiesmentioning

confidence: 99%

Dark energy and accelerating cosmological evolution from osculating Barthel-Kropina geometry

Hama,

Harko,

Sabau

2022

Preprint

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Finsler geometry is an important extension of Riemann geometry, in which to each point of the spacetime manifold an arbitrary internal variable is associated. Interesting Finsler geometries, with many physical applications, are the Randers and Kropina type geometries, respectively. A subclass of Finsler geometries is represented by the osculating Finsler spaces, in which the internal variable is a function of the base manifold coordinates only. In an osculating Finsler geometry one introduces the Barthel connection, which has the remarkable property that it is the Levi-Civita connection of a Riemannian metric. In the present work we consider the gravitational and cosmological implications of a Barthel-Kropina type geometry. We assume that in this geometry the Ricci type curvatures are related to the matter energy-momentum tensor by the standard Einstein equations. The generalized Friedmann equations in the Barthel-Kropina geometry are obtained by considering that the background Riemannian metric is of Friedmann-Lemaitre-Robertson-Walker type. The matter energy balance equation is also derived. The cosmological properties of the model are investigated in detail, and it is shown that the model admits a de Sitter type solution, and that an effective dark energy component can also be generated. Several cosmological solutions are also obtained by numerically integrating the generalized Friedmann equations. A comparison of two specific classes of models with the observational data and with the standard ΛCDM model is also performed, and it turns out that the Barthel-Kropina type models give a satisfactory description of the observations.

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Section: A Metric and Thermodynamic Quantitiesmentioning

confidence: 99%

Dark energy and accelerating cosmological evolution from osculating Barthel-Kropina geometry

Hama,

Harko,

Sabau

2022

Preprint

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“…respectively. 7 Our last step is to plug these results back into the Friedmann equations (see expressions (55a) and (55b) above) and in so doing arrive at…”

Section: Generalized Unconstrained Hyperfluidmentioning

confidence: 99%

“…Naturally, such fundamental modifications have a strong impact on the cosmic evolution and alter the Friedmann equations in a non-trivial manner [4]. For instance, in [5][6][7] and also in [8], it was shown that torsion can drastically alter the cosmological evolution and provide intriguing new results. From the geometrical point of view, torsion reflects the fact that the parallel transport of two vectors along each other does not form a closed parallelogram.…”

Section: Introductionmentioning

confidence: 99%

Friedmann-like universes with non-metricity

Iosifidis¹,

Vogiatzis²,

Tsagas³

2022

Preprint

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We study the potential effects of spacetime non-metricity in cosmology. In the spirit of Einstein-Cartan gravity, but with non-metricity replacing torsion, we consider the Einstein-Hilbert action and assume zero torsion. Adopting certain hyperfluid models, with non-vanishing hypermomentum that can source spacetime non-metricity, we add a matter component into the action and derive the field equations, along with the conservation laws. Applying our formulae to cosmology, we generalize the Friedmann and the Raychaudhuri equations in the presence of non-metricity. Our results show that, in a number of cases, non-metricity can mimic the effects of matter with unconventional equation of state. For instance, specific types of hypermomentum are found to act as an effective stiff fluid, thus opening the possibility that non-metricity could have played a significant role in the early stages of the universe's evolution. Alternative forms of hypermomentum can dominate the universal dynamics at late times. In either case, the equilibrium moment depends on the initial conditions and it is determined by a simple relation between the matter component and the hyperfluid.

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“…Different restrictions of non-Riemannian geometry provide distinct frameworks for gravity theories formulations and the inclusion of torsion and non-metricity in gravitational theories has led to many fruitful applications in various areas of both mathematics and physics, among which, for instance, the ones recently presented in [6][7][8][9][10][11][12][13][14][15]. In particular, in the cosmological context, in [15] the most general form of acceleration equation in the presence of torsion and non-metricity was derived and conditions under which torsion and non-metricity accelerate/decelerate the expansion rate of the Universe were discussed.…”

Section: Introductionmentioning

confidence: 99%

“…These terms have exactly the same dimension as R, that is [L −2 ], and therefore their inclusion is well motivated 2. In[11] (see also[12][13][14], where the form of torsion presented in[11] was constrained), where only the Ricci scalar was present in the gravitational action, the conservation law for hypermomentum was trivialized leaving, therefore, the torsion function fully undetermined. It will be shown in the sequel that the very presence of the quadratic torsion terms fixes this indeterminacy, providing exact evolution laws for all variables.…”

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confidence: 99%

The cosmology of quadratic torsionful gravity

Iosifidis

Ravera

2021

Eur. Phys. J. C

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We study the cosmology of a quadratic metric-compatible torsionful gravity theory in the presence of a perfect hyperfluid. The gravitational action is an extension of the Einstein–Cartan theory given by the usual Einstein–Hilbert contribution plus all the admitted quadratic parity even torsion scalars and the matter action also exhibits a dependence on the connection. The equations of motion are obtained by regarding the metric and the metric-compatible torsionful connection as independent variables. We then consider a Friedmann–Lemaître–Robertson–Walker background, analyze the conservation laws, and derive the torsion modified Friedmann equations for our theory. Remarkably, we are able to provide exact analytic solutions for the torsionful cosmology.

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Cosmological inflation driven by a scalar torsion function

Cited by 18 publications

References 32 publications

Dark energy and accelerating cosmological evolution from osculating Barthel-Kropina geometry

Dark energy and accelerating cosmological evolution from osculating Barthel-Kropina geometry

Friedmann-like universes with non-metricity

The cosmology of quadratic torsionful gravity

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