The cosmological behavior and the statefinder diagnosis for the New Tsallis agegraphic dark energy

In this work, we have considered the recently proposed new Tsallis agegraphic dark energy (NTADE) model [Mod. Phys. Lett. A 34, 1950086 (2019)] within the framework of a flat Friedmann–Robertson–Walker (FRW) Universe by taking various values of the parameter [Formula: see text]. The NTADE model shows the current phase transition of the Universe from decelerated to accelerated phase. The NTADE equation of state (EoS) parameter shows a rich behavior as it can be quintessence-like or phantom-like depending on the value of [Formula: see text]. For discriminating the NTADE model from [Formula: see text]CDM, we have plotted the statefinder parameters [Formula: see text], [Formula: see text] and [Formula: see text], [Formula: see text] pair. The NTADE model shows distinct evolutionary trajectories of their evolution in ([Formula: see text]) and ([Formula: see text]) plane. An analysis using the snap parameter and the [Formula: see text] pair dynamical analysis have also been performed.

Statefinder diagnostic for exponential harmonic field

The dynamic study of the harmonic exponential field has been made using the statefinder diagnostic. By the use of a specific method, we find out the statefinder parameters [Formula: see text], [Formula: see text] according to the deceleration parameter and the redshift. The numerical analysis of these parameters brings out the transition between the accelerated and decelerated phases of the universe. There is also an attracting effect from the SCDM (Standard Cold Dark Matter) model toward the LCDM model ([Formula: see text]CDM). In view of the results this study allows us to classify the exponential harmonic field among the quintessential models.

Statefinder diagnosis for Tsallis agegraphic dark energy model with ωD − ωD′ pair

A new class of dark energy model, known as “Tsallis agegraphic dark energy (TADE),” has been proposed using the holographic principle and Tsallis nonextensive entropy (Mod. Phys. Lett. A, 2019), considering the conformal time as well as the age of the Universe as IR cutoffs in flat Universe. The trajectories for evolution of statefinder parameters in [Formula: see text], [Formula: see text], [Formula: see text] and the [Formula: see text] planes are plotted for the TADE 1 and TADE 2 models for the value of the Tsallis parameter [Formula: see text], and taking the TADE energy density parameter [Formula: see text], according to the Planck 2018 results VI — [Formula: see text]CDM observational data without interaction.

Reconstructing f(T) Modified Gravity from ECHDE and ECNADE Models

We investigate alternative candidates to dark energy that can explain the current state of the universe in the framework of the generalized teleparallel theory of gravity f(T ) where T denotes the torsion scalar. To achieve this, we carried out a series of reconstruction taking into account to the ordinary and entropy-corrected versions of the holographic and new agegraphic dark energy models. These models used as alternative to dark energy in the literature in order describe the current state of our universe. It is remarked that the models reconstructed indicates behaviors like phantom or quintessence models. Furthermore, we also generated the EoS parameters associated to entropy-corrected models and we observed a transition phase between quintessence state and phantom state as showed by recent observational data. We also investigated on the stability theses models and we created the {r − s}. The behavior of certains physical parameters as speed of sound and the Statefinder parameters are compatible with current observational data.

Dynamical Properties of Dark Energy Models in Fractal Universe

In this paper, we consider the flat FRW spacetime filled with interacting dark energy and dark matter in fractal universe. We work with the three models of dark energy named as Tsallis, Renyi and Sharma–Mittal. We investigate different cosmological implications such as equation of state parameter, squared speed of sound, deceleration parameter, statefinder parameters, ω e f f - ω e f f ´ (where prime indicates the derivative with respect to ln a , and a is cosmic scale factor) plane and Om diagnostic. We explore these parameters graphically to study the evolving universe. We compare the consistency of dark energy models with the accelerating universe observational data. All three models are stable in fractal universe and support accelerated expansion of the universe.

A look into the cosmological consequences of a dark energy model with higher derivatives of H in the framework of Chameleon Brans–Dicke cosmology

In this paper, we study some relevant cosmological features of a Dark Energy (DE) model with Granda–Oliveros cut-off, which is just a specific case of Nojiri–Odintsov holographic DE [S. Nojiri and S. D. Odintsov, Gen. Relativ. Gravit. 38 (2006) 1285] unifying phantom inflation with late-time acceleration, in the framework of Chameleon Brans–Dicke (BD) cosmology. Choosing a particular ansatz for some of the quantities involved, we derive the expressions of some important cosmological quantities, like the Equation of State (EoS) parameter of DE [Formula: see text], the effective EoS parameter [Formula: see text], the pressure of DE [Formula: see text] and the deceleration parameter [Formula: see text]. Moreover, we study the behavior of statefinder parameters [Formula: see text] and [Formula: see text], of the cosmographic parameters [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] and of the squared speed of the sound [Formula: see text] for both case corresponding to noninteracting and interacting Dark sectors. We also plot the quantities we have derived and we calculate their values for [Formula: see text] (i.e. for the beginning of the universe history), for [Formula: see text] (i.e. for far future) and for the present time, indicated with [Formula: see text]. The EoS parameters have been tested against various observational values available in the literature.

A study of pilgrim dark energy model in Brans–Dicke theory

In this paper, we study the behavior of non-interacting and interacting pilgrim dark energy (DE) for non-flat FRW model in Brans–Dicke (BD) theory. We consider the future event horizon as well as logarithmic form of BD scalar field [Formula: see text], where [Formula: see text], [Formula: see text] and [Formula: see text] is the scale factor. We evaluate some well-known cosmological parameters such as equation of state as well as deceleration parameter and [Formula: see text] plane as well as statefinder parameters. We discuss graphical behavior of these parameters through pilgrim DE parameter [Formula: see text] for both non-interacting as well as interacting case with interacting parameter [Formula: see text]. It is found that the equation of state parameter gives consistent results with the current cosmic behavior while the deceleration parameter represents transition from decelerated to accelerated phase. The cosmological planes represent different DE regions. Finally, we discuss stability of the model through squared speed of sound in both cases.

A time-varying deceleration parameter for unified description of cosmological evolution

In this paper, we propose a new time-varying deceleration parameter for the description of a unified cosmological evolution (early inflation, deceleration and present acceleration) using Padé approximation. Within the background of Einstein’s general relativity and for a spatially flat homogeneous and isotropic model, the proposed deceleration parameter leads to a variable equation of state of effective matter that serves all matter within EoS [Formula: see text] (quintessence, relativistic and non-relativistic baryonic matter, stiff matter and cosmological constant), exactly in the same order as it required for various evolutionary phases of the universe. We consider a minimally coupled scalar field with self-interacting potential as the only matter source in the universe. The adopted scheme allows us to determine the potential for the scalar field that drives the cosmological evolution proposed by the deceleration parameter. We perform an explicit numerical computation where analytical solutions are not possible. We examine the validity of the model by depicting the statefinder parameters and comparing them with the recent observational outcomes of cosmography.

Statefinder diagnostic for a generalized Proca model

In this paper, we apply the statefinder diagnostic on the cosmology in the framework of the generalized Proca theories with derivative self-interactions possessing three propagating physical degrees of freedom. We discuss the evolving trajectories of the statefinder parameters with the parameter n of this model recently fitted as n = 0.254 and n = 0.16 by use of the current observational data and find that some typical characteristic of the evolution of statefinder parameters makes the model distinguishable between n = 0.254 case and n = 0.16 case and also from other dark energy models.