Cosmological analysis of scalar field models in f(R, T) gravity

The late time crossover from a power-law to an exponential expansion of the Universe evolution is the major problem in today’s physical cosmology. Unless this critical transition problem is solved, it is not possible to reach a holistic theory of cosmology. In this study, we propose a simple model in the FLRW framework, where dark matter and dark energy interact through a potential. We analytically solve this model and obtain scale factor a(t) from the presented model. Mainly, employing numerical solutions we show that the scale parameter has a hybrid form which includes power and exponential terms. The numerical results clearly show that there is a time crossover tc in the scale factor a(t) curve, which indicates the transition from the power-law to the exponential expansion of the Universe. We fit these unscaled curves and obtain that scale factor behaves as a(t) ∝ t 2/3 below t ≤ tc, and as a(t) ∝ exp(H0t) with H0 = 0.4 and H0 = 0.3 for the relatively weak and strong interactions above t > tc, respectively. It is the first time that we explicitly obtain a hybrid scale factor incorporating the power and exponential terms as a(t) ∝ t 2/3 e H0t . We conclude that the presented model can solve the late time transition problem of the Universe based on dark matter and dark energy interaction. Additionally, we numerically obtain other kinematic parameters depending upon the scale factor. We discuss the limit behaviors of all relevant cosmological parameters. Our results are completely in good agreement with observational data. Finally, we state that this work makes essential steps towards solving a critical outstanding problem of the cosmology, and has a potential to creates a paradigm for future studies in this field.

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“…where M is the matrix obtained from the coefficients of field equations in (14). To find an appropriate solution of the Eq.…”

Section: Lagrangian and Its Solutionsmentioning

confidence: 99%

“…Although numerous models have been proposed to explain this phenomenon, this transition still has not been explained consistently Refs. [11][12][13][14][15][16][17][18][19][20]. Without understanding this critical transition, it seems to be unlikely to proceed toward a comprehensive theory of cosmology.…”

Section: Introductionmentioning

confidence: 99%

Late time transition in the evolution of the Universe

Aydıner

Öz

Dereli

et al. 2021

Preprint

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“…So, already taking into account the presence of the functions u, v -describing the connection between the curvature scalar and the torsion scalar, which should help to give in the limit, respectively, the general theory of relativity or teleparallelgravity [12][13][14][15] is already so difficult to compute that researchers often try to describe the solution without taking into account these functions [16]. As a first approximation, it is possible to take into account these components as functions of the scale factor and its first time derivative.…”

Section: Introductionmentioning

confidence: 99%

Exact solution of the fiels equation of the generalized cosmological F(R,T) model

Yerzhanov

Abilmazhinova

2021

phst

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We considered cosmological model within the framework of the generalized F(R,T) gravity in flat FLRW metric. Earlier, an exponential solution was shown for the generalized case, which describes the inflationary stage of the evolution of the Universe. In this paper, it is shown that for the particular case of the Starobinsky model, the generalized model has, among other things, a power-law solution that describes the dust-like stage and the stage of radiation dominance. It should be noted that this solution was obtained by the analytical method as a solution to the Euler-Lagrange equation for this model, taking into account the functions u, v -describing the relationship between the curvature scalar and the torsion scalar, and depending not only on the first, but also on the second time derivative of the scale factor. This solution is of interest, since it shows not only that this model has a solution, but also that this solution can describe the modern observable Universe for more complex forms u, v than described earlier. This solution allows other related cosmological parameters to be obtained accordingly. The paper presents the parameter for the equation of state, which describes the stage of the evolution of the Universe.

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“…Although numerous models have been proposed to explain this phenomenon, this transition still has not been explained consistently Refs. [11][12][13][14][15][16][17][18][19][20][21]. Without understanding this critical transition, it seems to be unlikely to proceed toward a comprehensive theory of cosmology.…”

Section: Introductionmentioning

confidence: 99%

The hybrid scale factor, the transition from the matter dominated era to the dark energy dominated era and time evolution of the Universe

Aydıner

Basaran-Oz

Dereli

et al. 2021

Preprint

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The late time crossover from matter dominated era (represented power-law evolution) to the dark energy dominated era (represented exponential evolution) of the Universe evolution is the major problem in today’s physical cosmology. Unless this critical transition problem is solved, it is not possible to reach a holistic theory of cosmology. To explain this critical transition we propose a new model where the dark matter and dark energy interacting through a potential. Based on the FLRW framework we analytically solve this model and obtain the scale factor a(t). In addition, we numerically compute all cosmological quantities. We find more significant results to enlightening the physical mechanism of the critical transition. Firstly, we show that the scale factor a(t) has a hybrid form as a(t) = a0(t/t0) α e ht/t0 . This is main and important result in the presented work, which clearly indicates that the transition from the power-law to the exponential expansion of the Universe. The numerical results clearly provide that there is a time crossover tc in the scale factor a curve, which indicates the transition from the power-law to the exponential expansion of the Universe. Below t/t0 ≤ tc, matter era dominated hence time evolution of the Universe is given by a(t) ∝ (t/t0) α , on the other hand, above t/t0 > tc, the evolution is represented by a(t) ∝ exp(ht/t0). It is first time, the hybrid result for scale factor is exactly obtained from the presented model without use any approximation. Secondly, we fit the scale factor below and above tc. Surprisingly, we find that the scale factor behaves as a(t) ∝ (t/t0) 2/3 below t/t0 ≤ tc, and as a(t) ∝ exp(ht/t0) which indicates that the Hubble parameter takes the value in the interval of the around H0 = 69.5 and H0 = 73.5 km s−1Mpc−1 depend on the weak and strong interactions between dark components above t/t0 > tc, respectively. These are remarkable that α = 2/3 is completely consistent exact solution of the FLRW and re-scaled Hubble parameter H0 is the observable intervals given by Planck, CMB and SNIa data (or other combinations) for chosen interaction values are purely consistent with cosmological observations. Thirdly, we find from the model the transition point from matter dominated era to the dark energy dominated era in the cosmic time is the t0 = 9.8 Gyear which is consistent with the theoretical solution and observations. Additionally, we numerically obtain and analyse other cosmological quantities such as dimensionless Hubble parameter h, deceleration parameter q, jerk parameter j and EoS parameter w. We show that all cosmological quantities of this model are consistent observational results for the matter and dark energy dominated eras. As a result, we consider late time crossover of the Universe, we propose an interacting dark matter and dark energy model, we show that this model can explain the late time crossover phenomena of the Universe and our solutions are very good consistent with theoretical and observational results. Finally, we state that this work makes essential steps towards solving a critical outstanding problem of the cosmology, and has a potential to creates a paradigm for future studies in this field. Furthermore, the model also sheds light on the interaction mechanism of dark matter and dark energy in the Universe.

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Cosmological analysis of scalar field models in f(R, T) gravity

Cited by 44 publications

References 43 publications

Late time transition in the evolution of the Universe

Late time transition in the evolution of the Universe

Exact solution of the fiels equation of the generalized cosmological F(R,T) model

The hybrid scale factor, the transition from the matter dominated era to the dark energy dominated era and time evolution of the Universe

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