scholarly journals Growth rate and configurational entropy in Tsallis holographic dark energy

2021 ◽  
Vol 81 (3) ◽  
Author(s):  
Snehasish Bhattacharjee

AbstractIn this work, we analyzed the effect of different prescriptions of the IR cutoffs, namely the Hubble horizon cutoff, particle horizon cutoff, Granda and Oliveros horizon cut off, and the Ricci horizon cutoff on the growth rate of clustering for the Tsallis holographic dark energy (THDE) model in an FRW universe devoid of any interactions between the dark Universe. Furthermore, we used the concept of configurational entropy to derive constraints (qualitatively) on the model parameters for the THDE model in each IR cutoff prescription from the fact that the rate of change of configurational entropy hits a minimum at a particular scale factor $$a_{DE}$$ a DE which indicate precisely the epoch of dark energy domination predicted by the relevant cosmological model as a function of the model parameter(s). By using the current observational constraints on the redshift of transition from a decelerated to an accelerated Universe, we derived constraints on the model parameters appearing in each IR cutoff definition and on the non-additivity parameter $$\delta $$ δ characterizing the THDE model and report the existence of simple linear dependency between $$\delta $$ δ and $$a_{DE}$$ a DE in each IR cutoff setup.

2019 ◽  
Vol 97 (7) ◽  
pp. 726-734 ◽  
Author(s):  
M. Abdollahi Zadeh ◽  
A. Sheykhi

We consider the Brans–Dicke (BD) theory of gravity and explore the cosmological implications of the sign-changeable interacting holographic dark energy (HDE) model in the background of a Friedmann–Robertson–Walker (FRW) universe. As the system’s infrared cutoff, we choose the future event horizon, the Granda–Oliveros (GO), and the Ricci cutoffs. For each cutoff, we obtain the density parameter, the equation of state (EoS), and the deceleration parameter of the system. In case of future event horizon, we find out that the EoS parameter, wD, can cross the phantom line; as a result the transition from the deceleration to the acceleration of the Universe expansion can be achieved provided the model parameters are chosen suitably. We also investigate the instability of the sign-changeable interacting HDE model against perturbations in BD theory. For this purpose, we study the squared sound speed [Formula: see text] whose sign determines the stability of the model. When [Formula: see text] the model is unstable against perturbation. For future event horizon, our Universe can be stable ([Formula: see text]) depending on the model parameters. Then, we focus on GO and Ricci cutoffs and find out that although other features of these two cutoffs are consistent with observations, they cannot lead to stable dominated universe, except in a special case with GO cutoff. Our studies confirm that for the sign-changeable HDE model in the setup of BD cosmology, the event horizon is the most suitable horizon that can pass all conditions and leads to a stable dark-energy-dominated universe.


Author(s):  
Anirudh Pradhan ◽  
Gunjan Varshney ◽  
Umesh Kumar Sharma

This research explores the Tsallis holographic quintessence, k-essence, and tachyon model of dark energy in the modified f(R, T) gravity framework with Granda-Oliveros cutoff. We have analyzed the energy density through ρΛ = (αH<sup>2</sup> + βH)<sup>-δ+2</sup>. We study the correspondence between the quintessence, k-essence, and tachyon energy density with the Tsallis holographic dark energy density in a flat FRW Universe. The reconstruction is performed for the different values of Tsallis parameter δ in the region of ωΛ > -1 for the EoS parameter. This correspondence allows reconstructing the potentials and the dynamics for the scalar fields models, if we set some constraints for the model parameters, which describe the accelerated expansion of the Universe.


Author(s):  
Umesh Kumar Sharma ◽  
Vipin Chandra Dubey

In this work, we study the Rényi holographic dark energy (RHDE) model in a flat FRW Universe where the infrared cut-off is taken care by the Hubble horizon and also by taking three different parametrizations of the interaction term between the dark matter and the dark energy. Analyzing graphically, the behavior of some cosmological parameters in particular deceleration parameter, equation of state (EoS) parameter, energy density parameter and squared speed of sound, in the process of the cosmic evolution, is found to be leading towards the late-time accelerated expansion of the RHDE model. Also, we find the departure for the derived models from the standard [Formula: see text]CDM model according to the evolution of jerk parameter. Moreover, we compare the model parameters by considering the observational Hubble data which consist of 51 points in the redshift range [Formula: see text].


2012 ◽  
Vol 27 (16) ◽  
pp. 1250085 ◽  
Author(s):  
ZHUO-PENG HUANG ◽  
YUE-LIANG WU

A holographic dark energy model characterized by the conformal-age-like length scale [Formula: see text] is motivated from the four-dimensional space–time volume at cosmic time t in the flat Friedmann–Robertson–Walker (FRW) universe. It is shown that when the background constituent with constant equation of state wm dominates the universe in the early time, the fractional energy density of the dark energy scales as [Formula: see text] with the equation of state given by [Formula: see text]. The value of wm is taken to be wm≃-1 during inflation, wm = ⅓ in radiation-dominated epoch and wm = 0 in matter-dominated epoch, respectively. When the model parameter d takes the normal value at order one, the fractional density of dark energy is naturally negligible in the early universe, Ω de ≪1 at a ≪1. With such an analytic feature, the model can be regarded as a single-parameter model like the ΛCDM model, so that the present fractional energy density Ω de (a = 1) can solely be determined by solving the differential equation of Ωde once d is given. We further extend the model to the general case in which both matter and radiation are present. The scenario involving possible interaction between the dark energy and the background constituent is also discussed.


2012 ◽  
Vol 27 (20) ◽  
pp. 1250115 ◽  
Author(s):  
ZHENHUI ZHANG ◽  
MIAO LI ◽  
XIAO-DONG LI ◽  
SHUANG WANG ◽  
WEN-SHUAI ZHANG

In the original holographic dark energy (HDE) model, the dark energy density is proposed to be [Formula: see text], with c a dimensionless constant characterizing the properties of the HDE. In this work, we propose the generalized holographic dark energy (GHDE) model by considering the parameter c as a redshift-dependent function c(z). We derive all the physical quantities of the GHDE model analytically, and fit the c(z) by trying four kinds of parametrizations. The cosmological constraints of the c(z) are obtained from the joint analysis of the present SNLS3+BAO+CMB +H0data. We find that, compared with the original HDE model, the GHDE models can provide a better fit to the data. For example, the GHDE model with JBP-type c(z) can reduce the [Formula: see text] of the HDE model by 2.16. We also find that, unlike the original HDE model with a phantom-like behavior in the future, the GHDE models can present many more different possibilities, i.e. it allows the GHDE in the future to be either quintessence-like, cosmological constant-like, or phantom-like, depending on the forms of c(z).


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