Analysis with observational constraints in $$ \Lambda $$ Λ -cosmology in f(R, T) gravity

Nagpal, Ritika; Pacif, S. K. J.; Singh, J. K.; Bamba, Kazuharu; Беешам, Ароонкумар

doi:10.1140/epjc/s10052-018-6403-y

“…For this, it is better to write the expressions of cosmological parameters in terms of redshift z. For a detailed study of these kinds of model building/ reconstructions, one can refer to some recent papers [44], [45], [46], [47], [48], [49], [50], [51] in different scenarios.…”

Section: Solution Of Field Equationsmentioning

confidence: 99%

Reconstructing cosmic evolution with a density parametrization

Nagpal,

Pacif,

Parida

2022

Preprint

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0

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The current paper provides a comprehensive examination of a dark energy cosmological model in the classical regime, in which a generic scalar field is regarded as a dark energy source. Einstein's field equations are solved in model independent way i.e. using a scheme of cosmological parametrization. A parametrization of the density parameter as a function of the cosmic scale factor has been investigated in this line. The result is noteworthy because it shows a smooth transition from a decelerating to an accelerating phase in the recent past. The model parameters involved in the functional form of the parametrization approach utilized here were constrained using certain external datasets. The updated Hubble datasets containing 57 datapoints, 1048 points of recently compiled Pantheon datasets, and also the Baryon Acoustic Oscillation (BAO) datasets are used here to determine the best-fitting model parameter values. The expressions of several significant cosmological parameters are represented as a function of redshift 'z' and illustrated visually for the best fit values of the model parameters to better comprehend cosmic evolution. The obtained model is also compared with the ΛCDM model. Our model has a distinct behavior in future and shown a big crunch type collapse. The best fit values of the model parameters are also used to compute the current values of several physical and geometrical parameters, as well as phase transition redshift. To examine the nature of dark energy, certain cosmological tests and diagnostic analyses are done on the derived model.

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“…A detailed analysis of the cosmological model based on the field equations R μν − (1/2)Rg μν = [(8π + λ)/λ]T μν + ( p + T /2)g μν was performed in [120]. The maximum likelihood analysis was used to obtain the constraints on the Hubble parameter H 0 and the model parameter by taking into account the observational Hubble data set H (z), the Union 2.1 compilation data set SNeIa, the Baryon Acoustic Oscillation data BAO, and the joint data set H (z) + SNeIa and H (z) + SNeIa + BAO, respectively.…”

Section: (Mat) μνmentioning

confidence: 99%

Generalizing the coupling between geometry and matter: $$f\left( R,L_m,T\right) $$ gravity

Haghani

¹

,

Harkó

²

2021

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We generalize and unify the $$f\left( R,T\right) $$ f R , T and $$f\left( R,L_m\right) $$ f R , L m type gravity models by assuming that the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar R, of the trace of the energy–momentum tensor T, and of the matter Lagrangian $$L_m$$ L m , so that $$ L_{grav}=f\left( R,L_m,T\right) $$ L grav = f R , L m , T . We obtain the gravitational field equations in the metric formalism, the equations of motion for test particles, and the energy and momentum balance equations, which follow from the covariant divergence of the energy–momentum tensor. Generally, the motion is non-geodesic, and takes place in the presence of an extra force orthogonal to the four-velocity. The Newtonian limit of the equations of motion is also investigated, and the expression of the extra acceleration is obtained for small velocities and weak gravitational fields. The generalized Poisson equation is also obtained in the Newtonian limit, and the Dolgov–Kawasaki instability is also investigated. The cosmological implications of the theory are investigated for a homogeneous, isotropic and flat Universe for two particular choices of the Lagrangian density $$f\left( R,L_m,T\right) $$ f R , L m , T of the gravitational field, with a multiplicative and additive algebraic structure in the matter couplings, respectively, and for two choices of the matter Lagrangian, by using both analytical and numerical methods.

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“…In 2011, Harko et al [66] widespread the sphere of this arbitrary coupling of scalar curvature R and trace T of EMT, and this introduces another modification in the GR known as f (R, T ) theory of gravity. A lot of notable works have already been carried out in f (R, T ) gravity [67], [68], [69], [70], [71], [72], [73], [74], [75], [76], [77], [78], [79], [80], [81] .…”

Section: Introductionmentioning

confidence: 99%

Cosmological aspects of $f(R,T)$ gravity in a simple model with a parametrization of $q$

Nagpal,

Pacif

2021

Preprint

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In this paper, we have considered a quadratic variation of the deceleration parameter (q) as a function of cosmic time (t) which describes a smooth transition from the decelerating phase of the Universe to an accelerating one and also show some distinctive feature from the standard model. The logical move of this article is against the behavior of the future Universe, i.e. whether the Universe expands forever or ends with a Big Rip, and we observe that the outcome of the considered parametrization comes in favor of Big Rip future of the Universe. The whole set up of the parametrization and solution is taken in f (R, T ) theory of gravity for a spatially flat Friedmann-Lemaître-Robertson-Walker (FLRW) geometry. Furthermore, we have considered the functional form of f (R, T ) function as f (R) + f (T ), where a quadratic correction of the geometric term R is adopted as the function f (R), and a linear matter term f (T ). We have investigated some features of the model by examining the behavior of physical parameters. Our primary goal here is to discuss the physical dynamics of the model in f (R, T ) gravity. We have found, the EoS parameter also has the same singularity as that of the Hubble parameter i.e. at the initial phase and at the Big Rip. The EoS parameter is explored in some detail for our choice of f (R, T ) function considered here. Different cases for f (R, T ) functional form for different values of the coupling parameters are discussed, and the evolution of the physical parameters is shown graphically.

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Analysis with observational constraints in $$ \Lambda $$ Λ -cosmology in f(R, T) gravity

Cited by 54 publications

References 117 publications

Reconstructing cosmic evolution with a density parametrization

Reconstructing cosmic evolution with a density parametrization

Generalizing the coupling between geometry and matter: $$f\left( R,L_m,T\right) $$ gravity

Cosmological aspects of $f(R,T)$ gravity in a simple model with a parametrization of $q$

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