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

Hama, Rattanasak; Harkó, Tiberiu; Sabau, Sorin V.

doi:10.1140/epjc/s10052-022-10318-9

Cited by 15 publications

(14 citation statements)

References 121 publications

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“…Hence, the extended Einstein equations become in this approach G µν = κ 2 T bar µν + κ 2 T (geom) µν (g µν , R, R, ...), where T µν is the energy-momentum tensor of ordinary matter, and T (geom) µν (g µν , R, R, ...) is a purely geometric term, obtained from the metric, torsion τ , nonmetricity Q, extensions of Riemann geometry etc., and which can effectively mimic dark energy, dark matter, or both. Some typical example of dark geometric theories are the f (R) [7], f (Q) [8], hybrid metric-Palatini gravity [9] theories, or gravitational theories based on the Weyl-Cartan-Weitzenböck [10], or Weyl [11,12], and Finsler geometries [13,14].…”

Section: Introductionmentioning

confidence: 99%

The first variation of the matter energy-momentum tensor with respect to the metric, and its implications on modified gravity theories

Haghani¹,

Harkó²

2023

Preprint

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The first order variation of the matter energy-momentum tensor Tµν with respect to the metric tensor g αβ plays an important role in modified gravity theories with geometry-matter coupling, and in particular in the f (R, T ) modified gravity theory. We obtain the expression of the variation δTµν/δg αβ for the baryonic matter described by an equation given in a parametric form, with the basic thermodynamic variables represented by the particle number density, and by the specific entropy, respectively. The first variation of the matter energy-momentum tensor turns out to be independent on the matter Lagrangian, and can be expressed in terms of the pressure, the energymomentum tensor itself, and the matter fluid four-velocity. We apply the obtained results for the case of the f (R, T ) gravity theory, where R is the Ricci scalar, and T is the trace of the matter energy-momentum tensor, which thus becomes a unique theory, also independent on the choice of the matter Lagrangian. A simple cosmological model, in which the Hilbert-Einstein Lagrangian is generalized through the addition of a term proportional to T n is considered in detail, and it is shown that it gives a very good description of the observational values of the Hubble parameter up to a redshift of z ≈ 2.5.

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Section: Introductionmentioning

confidence: 99%

The first variation of the matter energy-momentum tensor with respect to the metric, and its implications on modified gravity theories

Haghani¹,

Harkó²

2023

Preprint

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“…Candidate metric geometries that can intrinsically describe the motion a e-mail: manoliskapsabelis@yahoo.gr b e-mail: kevrekid@math.umass.edu c e-mail: pstavrin@math.uoa.gr d e-mail: alktrian@phys.uoa.gr (corresponding author) are the Finsler and Finsler-like geometries which constitute metrical generalizations of Riemannian geometry and depend on position and velocity/momentum/scalar coordinates. These are dynamic geometries that can describe locally anisotropic phenomena and Lorentz violations [5][6][7][8][9][10][11][12][13][14][15] as well as with field equations, FRW and Raychaudhuri equations, geodesics, dark matter and dark energy effects [16][17][18][19][20][21]. By considering this approach, the gravitational field is interpreted as the metric of a generalized spacetime and constitutes a force-field which contains the motion.…”

Section: Introductionmentioning

confidence: 99%

“…In the framework of applications of Finsler geometry, many works in different directions of geometrical and physical structures have contributed to the extension of research for theoretical and observational approaches during the last years. We cite some works from the literature of the applications of Finsler geometry [7,8,13,[21][22][23][24][25][26][27][28][29][30][31][32].…”

Section: Introductionmentioning

confidence: 99%

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Schwarzschild–Finsler–Randers spacetime: geodesics, dynamical analysis and deflection angle

2022

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In this work, we extend the study of Schwarzschi ld–Finsler–Randers (SFR) spacetime previously investigated by a subset of the present authors (Triantafyllopoulos et al. in Eur Phys J C 80(12):1200, 2020; Kapsabelis et al. in Eur Phys J C 81(11):990, 2021). We will examine the dynamical analysis of geodesics which provides the derivation of the energy and the angular momentum of a particle moving along a geodesic of SFR spacetime. This study allows us to compare our model with the corresponding of general relativity (GR). In addition, the effective potential of SFR model is examined and it is compared with the effective potential of GR. The phase portraits generated by these effective potentials are also compared. Finally we deal with the derivation of the deflection angle of the SFR spacetime and we find that there is a small perturbation from the deflection angle of GR. We also derive an interesting relation between the deflection angles of the SFR model and the corresponding result in the work of Shapiro et al. (Phys Rev Lett 92(12):121101, 2004). These small differences are attributed to the anisotropic metric structure of the model and especially to a Randers term which provides a small deviation from GR.

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“…In particular, in [121], the cosmological implications of the Kropina geometry have been investigated in detail, by using the mathematical formalism of the osculating Finsler spaces, in which the internal variable is a function of the base manifold coordinates only. Moreover, in order to describe gravitational phenomena, the Barthel connection was adopted, which has the remarkable property that it is the Levi-Civita connection of a Riemannian metric.…”

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Cosmological tests of the osculating Barthel–Kropina dark energy model

et al. 2023

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We further investigate the dark energy model based on the Finsler geometry inspired osculating Barthel–Kropina cosmology. The Barthel–Kropina cosmological approach is based on the introduction of a Barthel connection in an osculating Finsler geometry, with the connection having the property that it is the Levi-Civita connection of a Riemannian metric. From the generalized Friedmann equations of the Barthel–Kropina model, obtained by assuming that the background Riemannian metric is of the Friedmann–Lemaitre–Robertson–Walker type, an effective geometric dark energy component can be generated, with the effective, geometric type pressure, satisfying a linear barotropic type equation of state. The cosmological tests, and comparisons with observational data of this dark energy model are considered in detail. To constrain the Barthel–Kropina model parameters, and the parameter of the equation of state, we use 57 Hubble data points, and the Pantheon Supernovae Type Ia data sample. The st statistical analysis is performed by using Markov Chain Monte Carlo (MCMC) simulations. A detailed comparison with the standard $$\Lambda $$ Λ CDM model is also performed, with the Akaike information criterion (AIC), and the Bayesian information criterion (BIC) used as the two model selection tools. The statefinder diagnostics consisting of jerk and snap parameters, and the Om(z) diagnostics are also considered for the comparative study of the Barthel–Kropina and $$\Lambda $$ Λ CDM cosmologies. Our results indicate that the Barthel–Kropina dark energy model gives a good description of the observational data, and thus it can be considered a viable alternative of the $$\Lambda $$ Λ CDM model.

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

Cited by 15 publications

References 121 publications

The first variation of the matter energy-momentum tensor with respect to the metric, and its implications on modified gravity theories

The first variation of the matter energy-momentum tensor with respect to the metric, and its implications on modified gravity theories

Schwarzschild–Finsler–Randers spacetime: geodesics, dynamical analysis and deflection angle

Cosmological tests of the osculating Barthel–Kropina dark energy model

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