Studying the intervention of an unusual term in f(T) gravity via the Noether symmetry approach

Tajahmad, Behzad

doi:10.1140/epjc/s10052-017-5050-z

Cited by 19 publications

(18 citation statements)

References 62 publications

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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]. 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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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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Section: Introductionmentioning

confidence: 99%

Late time transition in the evolution of the Universe

Aydıner

Öz

Dereli

et al. 2021

Preprint

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“…Fig. 6 This figure demonstrates the plot of f (R) for four options of interest (1-Pure electromagnetic case (blue color); 2-Pure matter case (green color); 3-Both electromagnetic and matter cases (red color); 4-Vacuum case (orange color)) at curvature interval [13,35] of their amounts, satisfy this relation: em 9 > m + em 10 > vacuum 11 > m 12 (see Figs. 6,7,8).…”

Section: The Variable Jerk Case J = Q(t) (N = 3)mentioning

confidence: 82%

“…This mysterious candidate being incompatible with strong energy condition is dubbed as dark energy. This cosmic behavior can also be explained either by modifying matter part ( f (R) gravity, f (T ) gravity, f (T ) gravity with unusual term [9], scalartensor theories [10], etc.) or by modifying geometric part (chaplygin gas [11], quintessence [12], phantom [13], quintom [14], etc.)…”

Section: Introductionmentioning

confidence: 99%

Raychaudhuri-based reconstruction of anisotropic Einstein–Maxwell equation in 1+3 covariant formalism of f(R)-gravity

Tajahmad

2020

Eur. Phys. J. C

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Recently, a new strategy to the reconstruction of $$f(R)$$f(R)-gravity models based on the Raychaudhuri equation has been suggested by Choudhury et al. (MNRAS 485:5693, 2019). In this paper, utilizing this method, the reconstruction of anisotropic Einstein–Maxwell equation in the $$1+3$$1+3 covariant formalism of $$f(R)$$f(R)-gravity is investigated in four modes: (i) Reconstruction from a negative constant deceleration parameter refereeing to an ever-accelerating universe; (ii) Reconstruction from a constant jerk parameter $$j=1$$j=1 which recovers celebrated $$\varLambda \text {CDM}$$ΛCDM mode of evolution; (iii) Reconstruction from a variable jerk parameter $$j=Q(t)$$j=Q(t); and (iv) Reconstruction from a slowly varying jerk parameter. Furthermore, two suggestions for enhancing the method are proposed.

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“…As is observed, in the special case m = 1 (FRW), both are equal: n 1 = n 2 = 1/3 . It is important to mention that if one wants to examine FRW-case, then he must take k 1 = k 2 / √ 2 in (25). In this stage, we encounter a bifurcation in equations due to n , and therefore two classes are separated by it.…”

Section: Nother Symmetry Approach and Csss-trickmentioning

confidence: 99%

“…In this stage, we encounter a bifurcation in equations due to n , and therefore two classes are separated by it. Indeed, the suitable solutions obtained by Noether symmetry approach, do not allow to have a four-potential of the form (25), hence, it is readily observed that (25) must be split into two independent cases:…”

Section: Nother Symmetry Approach and Csss-trickmentioning

confidence: 99%

Late-time-accelerated expansion arisen from gauge fields in an anisotropic background and a fruitful trick for Noether’s approach

Tajahmad

2020

J. High Energ. Phys.

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In this paper, a modified teleparallel gravity action containing a coupling between a scalar field potential and magnetism, in anisotropic and homogeneous backgrounds, is investigated through Noether symmetry approach. The focus of this work is to describe late-time-accelerated expansion. Since finding analytical solutions carrying all conserved currents emerged by Noether symmetry approach, is very difficult, hence regularly in the literature, the authors split the total symmetry into sub-symmetries and then select, usually, some of them to be carried by the solutions. This manner limits the forms of unknown functions obtained. However, in ref.[68], B.N.S. approach was proposed in order to solve such problems but its main motivation was carrying more conserved currents by solutions. In this paper, by eliminating the aforementioned limitation as much as possible, a trick leading to some graceful forms of unknown functions is suggested. Through this fruitful approach, the solutions may carry more conserved currents than usual ways and maybe new forms of symmetries. I named this new approach to be CSSS-trick (Combination of Sub-symmetries through Special Selections). With this approach, it is demonstrated that the unified dark matter potential is deduced by the gauge fields. Utilizing the B-function method, a detailed data analysis of results obtained yielding perfect agreements with recent observational data are performed. And finally, the Wheeler-De Witt (WDW) equation is discussed to demonstrate recovering the Hartle criterion due to the oscillating feature of the wave function of the universe.

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Studying the intervention of an unusual term in f(T) gravity via the Noether symmetry approach

Cited by 19 publications

References 62 publications

Late time transition in the evolution of the Universe

Late time transition in the evolution of the Universe

Raychaudhuri-based reconstruction of anisotropic Einstein–Maxwell equation in 1+3 covariant formalism of f(R)-gravity

Late-time-accelerated expansion arisen from gauge fields in an anisotropic background and a fruitful trick for Noether’s approach

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