Holographic Dark Energy Model Research Articles

Reconstructing Tsallis holographic quintessence

Within the framework of quantum gravity and modified entropy-area formalism, the Tsallis holographic dark energy is an effort to peep into a mysterious content of the Universe, the dark energy, to analyze its nature. The Tsallis parameter [Formula: see text] provides the main characteristic of the Tsallis holographic dark energy. Opting the value of Tsallis parameter [Formula: see text], a quintessence scalar field description of the Tsallis holographic dark energy model can be obtained. In this work, we present this quintessential explanation of the Tsallis holographic dark energy with [Formula: see text] and reconstruct the dynamics of the scalar field and the potential of quintessence.

Constraints on holographic dark energy model with matter creation in Brans–Dicke theory and thermodynamic analysis

The adiabatic matter creation for a spatially flat, homogeneous and isotropic universe is discussed in holographic dark energy (HDE) in the context of Brans–Dicke theory. Since the HDE density is considered as a dynamical cosmological constant, it is natural to study it in a dynamical frame of Brans–Dicke theory. We show that HDE model with matter creation, whose infrared cutoff is set by the Hubble horizon, leads to solution that unify the early and late time acceleration. The latest observational data from supernovae (Pantheon sample), Hubble H ( z ) and latest local H 0 by SH0ES are used for constraining the model parameters. Using the Markov chain Monte Carlo method, we obtain the best fit values of the parameters for different models. It is found that the HDE model without matter creation does not achieve transition phase when the Hubble horizon is taken as an IR cut-off. However, it achieves the phase transition from decelerated phase to accelerated phase with same IR cut-off with the inclusion of gravitationally induced matter creation. The best fit values of HDE model with matter creation are fitted very well in Hubble error data. Using AIC and BIC, and geometrical diagnostic parameters, we compare the models with Λ CDM model and discuss the viability of the model. A detailed thermodynamic analysis is also carried out.

Models of holographic dark energy in f(Q) gravity

Present analysis dedicated to the dynamical investigation of models of holographic dark energy using FLRW cosmological model in the context of modified gravity in which Lagrangian be the arbitrary function of the trace of the non-metricity tensor Q say f ( Q ) gravity where the nonmetricity Q is responsible for the gravitational interaction. We govern the features of the derived cosmological model in view of the relation between cosmic time and redshift as t = 1 α k l o g 1 + 1 ( 1 + z ) α and discuss the evolution trajectories of the equation of state parameter and stability parameters in the evolving universe. The classification of the field equations toward f ( Q ) = Q + m Q n makes available that the model is purely accelerating corresponds to 0 ≤ q ≤ − 1 .

Comparing entropy inspired holographic dark energy models through statefinder hierarchy and growth rate of perturbations

In this paper, we have investigated some recently proposed entropy-based versions of various HDE models, namely, the TADE, THDE, RHDE and SMHDE for different values of model parameter [Formula: see text] with the help of two diagnostic tools, in the context of a flat Friedmann–Lema[Formula: see text]tre–Robertson–Walker Universe. The statefinder hierarchy is the first diagnostic tool, by which we examine these DE models. The evolution of statefinder hierarchy parameters [Formula: see text], [Formula: see text] [Formula: see text], [Formula: see text] has been investigated by plotting against redshift [Formula: see text]. The evolutionary trajectories of all the DE models approach the [Formula: see text]CDM model, except the TADE model for some values of [Formula: see text] at late time, are well discriminated with the [Formula: see text]CDM model at early time. To get more clear discrimination among the DE models at late time, we have used the CND, i.e. [Formula: see text][Formula: see text], where [Formula: see text] indicates the fractional growth parameter. The evolutionary trajectories of [Formula: see text] and [Formula: see text] show different characteristics and the departure from [Formula: see text]CDM could be well evaluated.

Cosmological consequences of Rényi, Sharma–Mittal holographic and new agegraphic dark energy models in generalized Rastall gravity

The main motivation of our study is to explore Rényi holographic dark energy, Sharma–Mittal holographic dark energy, Rényi new agegraphic dark energy, and Sharma–Mittal new agegraphic dark energy in the context of generalized Rastall gravity with the two-fluid system, dark energy, and dark matter. In this regard, we have considered the scale factors into two distinct categories, one of which corresponds to the future singularity, whereas the other represents initial singularity. By employing future event horizon as infrared (IR)-cutoff, different cosmological quantities like deceleration parameter, equation of state (EoS) parameter are evaluated, and their ramifications have been described graphically. Analyzing the squared speed of sound, we have seen classically stable and unstable behavior for each of the considered models. Finally, we study [Formula: see text]–[Formula: see text] plane and find the thawing/freezing regions.

Study of growth matter index and cosmic implications in dynamical Chern\u2013Simons modified gravity

In the framework of dynamical Chern–Simons theory of gravity, we study the recent cosmic expansion with acceleration of the universe. We take interacting scenario of dark energy and dark matter with three cutoffs like Granda–Oliveros, higher order derivative of Hubble parameter and generalized holographic dark energy model. In the flat Friedmann–Robertson–Walker universe, well-known cosmological parameters have been calculated. We study the perturbation of matter density growth, growth factor and growth index behavior for the underlying framework. The cosmological parameters like equation of state parameter, deceleration parameter, and stability of each model are discussed. The outcomes of these models represent the cosmic expansion of the universe with acceleration.

Braneworld Inspires Cosmological Implications of Barrow Holographic Dark Energy

In the present manuscript, the evolution of the cosmic parameters and planes are being investigated in the framework of the DGP braneworld model. In this scenario, the interaction Γ between the Barrow holographic dark energy model (whose infrared cutoff scale is set by Hubble and event horizons) and pressureless dark matter are considered. We check the behavior of different cosmological parameters such as Hubble, equation of state, deceleration and squared speed of sound from the early matter-dominated era until the late-time acceleration. It is found that the range of Hubble parameter lies in the interval 95−35+35 (for Hubble horizon) and 97−23+23 (for event horizon). For both horizons, the equation of state parameter favors the phantom dominant era as well as the ΛCDM model while the deceleration parameter illustrates the accelerated expansion of the universe. Furthermore, stability of the underlying model is found through squared speed of sound. Furthermore, it is observed that ω−ωϑ′ plane corresponds to freezing and thawing region for Hubble and event horizons, respectively. Furthermore, statefinder plane shows the ΛCDM and Chaplygin gas behavior for both models. Finally, we investigate the thermodynamical nature of the underlying model through Barrow entropy as horizon entropy and found validity for both horizons.

A dynamical system approach to the holographic dark energy in a modified theory of gravity

In this paper, we carry a dynamical system analysis of a holographic dark energy model of a modified theory of gravity based on braneworld scenario. The infra-red cutoff of the holographic dark energy is considered to be the Hubble scale in a first approach and the Ricci scalar curvature scale in a second approach. We present a detailed analysis of the critical points, their stability and the late-time cosmological viability of the solutions in the phase space. For both holographic dark energy models, we investigate the case of a noninteracting braneworld and extend our analysis to the interacting case between dark energy and cold dark matter by considering some specific forms of interaction.

An effective field theory of holographic dark energy

A general covariant local field theory of the holographic dark energy model is presented. It turns out the low energy effective theory of the holographic dark energy is the massive gravity theory whose graviton has 3 polarisations, including one scalar mode and two tensor modes. The Compton wavelength is the size of the future event horizon of the universe. The UV-IR correspondence in the holographic dark energy model stems from the scalar graviton's strong coupling at the energy scale that marks the breaking down of the effective field theory.

A new comparison between holographic dark energy and standard varLambda -cosmology in the context of cosmography method

The cosmography method is a model-independent technique used to reconstruct the Hubble expansion of the Universe at low redshifts. In this method, using the Hubble diagrams from Type Ia Supernovae (SNIa) in Pantheon catalog, quasars and Gamma-Ray Bursts (GRB), we put observational constraints on the cosmographic parameters in holographic dark energy (HDE) and concordance varLambda CDM models by minimizing the error function chi ^2 based on the statistical Markov Chain Monte Carlo (MCMC) algorithm. Then, we compare the results of the models with the results of the model-independent cosmography method. Except for the Pantheon sample, we observe that there is a big tension between standard cosmology and Hubble diagram observations, while the HDE model remains consistent in all cases. Then we use different combinations of Hubble diagram data to reconstruct the Hubble parameter of the model and compare it with the observed Hubble data. We observe that the Hubble parameter reconstructed from the model-independent cosmography method has the smallest deviation from the Hubble data and the varLambda CDM (HDE) model has the largest (middle) deviation, especially when we keep the observational data point 226^{+8.0}_{-0.8} at redshift z=2.36 in the analysis. On the contrary, in the redshift z <1, we see that the compatibility of varLambda CDM cosmology and observation is even better than the model independent cosmography method.

Diagnosing the Sharma–Mittal Holographic Dark Energy Model through the Statefinder

Diagnosing the Sharma–Mittal Holographic Dark Energy Model through the Statefinder

Higher dimensional phantom dark energy model ending at a de-Sitter phase

In this work, using a spherically symmetric metric, we investigate a minimally interacting holographic dark energy model within the framework of the Saez-Ballester Theory. We predict that the dark energy component dominating the universe is of phantom type, which will lead the model universe to cosmic doomsday (big rip singularity). As the big rip singularity and holographic dark energy are incompatible with each other, we employ a higher dimensional scenario so that the cosmic doomsday is replaced by a de-Sitter phase. The model expands with a slow and uniform change of size during the early evolution, whereas the change becomes faster and faster, agreeing with the present observation of the accelerated expansion. The present values of the Hubble parameter and the dark energy EoS parameter are found to be H=67 and λ=−1.00011, which agree with the respective values H0=67.36±0.54kms−1Mpc−1and λ=−1.03±0.03 of the most recent Planck 2018 result.

Tsallis holographic dark energy models in Bianchi type space time

The main purpose of this paper is to construct interacting and non-interacting Tsallis holographic dark energy models in an anisotropic and homogeneous Bianchi type-VI0 space time within the framework of a scalar tensor theory proposed by Saez and Ballester (1986). For this purpose, we use the relationship between metric potentials of the model and varying deceleration parameter to solve the Saez–Ballester field equations. In order to study the physical behavior of the models, we obtain some well-known cosmological parameters like deceleration, equation of state, statefinder, Om diagnostic parameters, and ωT - ωT′ planes of the models. Also, we observe that in our non-interacting and interacting models deceleration and equation of state parameters support the recent observational data.

Amended FRW Metric and Rényi Dark Energy Model

This article is devoted to exploring the Rényi holographic dark energy model in the theory of Chern-Simons modified gravity. We studied the deceleration parameter, equation of state, and cosmological plane considering the Amended FRW modal. Modified field equations of -gravity theory gave two independent solutions. In the first case, this model provided the transitional change from deceleration to acceleration compatible with collected observational data. However, it supported a decelerating phase of expansion only in the second case. It was noted that the Equation of State advocated the dominance era under the influence of dark energy in the first case and the second predicted the influence of Λ CDM. In both cases, ω &lt; 0 , ω ′ &lt; 0 voted that the universe is in a freezing region and its cosmic expansion is more rapidly accelerated in the background of Chern-Simons modified gravity.

Tsallis holographic dark energy model with observational constraints in the higher derivative theory of gravity

The present study deals with a Tsallis holographic dark energy model in a flat Friedmann-Lamatire-Rbertson-Walker space-time geometry in the context of higher derivative theory of gravity. We have solved the field equations by applying energy conservation-law in non-interacting case and have obtained such a scale factor a(τ)=[sinh(2a1τ)]12 where a1 is called as model parameter which shows transit phase evolution of the universe (decelerating to accelerating). Using this scale factor we have obtained the various cosmological parameters viz. Hubble parameter H, deceleration parameter (DP) q, jerk j, snap s, lerk l and max-out m. Constraining on Hubble parameters H(z) by the observational data of H(z) we have obtained the present values of H0, a0 and a1 and by using these constrained values, we have studied other cosmological parameters. Taking the constant equation of state (EoS) ωm for ordinary matter, we have investigated the effective behaviour of various cosmological parameters and energy conditions in our model. We have observed the present values of {t0,H0,q0,j0,s0,l0,m0,ωde0,ω0(eff)} and discussed with ΛCDM model. We have found the age of the present universe t0=13.05 Gyrs, present value of DP q0=−0.8065 and transition point zt=0.748 which are compatible with several observational results.

Different Faces of Generalized Holographic Dark Energy

In the formalism of generalized holographic dark energy (HDE), the holographic cut-off is generalized to depend upon LIR=LIRLp,L˙p,L¨p,⋯,Lf,L˙f,⋯,a with Lp and Lf being the particle horizon and the future horizon, respectively (moreover, a is the scale factor of the Universe). Based on such formalism, in the present paper, we show that a wide class of dark energy (DE) models can be regarded as different candidates for the generalized HDE family, with respective cut-offs. This can be thought as a symmetry between the generalized HDE and different DE models. In this regard, we considered several entropic dark energy models—such as the Tsallis entropic DE, the Rényi entropic DE, and the Sharma–Mittal entropic DE—and found that they are indeed equivalent with the generalized HDE. Such equivalence between the entropic DE and the generalized HDE is extended to the scenario where the respective exponents of the entropy functions are allowed to vary with the expansion of the Universe. Besides the entropic DE models, the correspondence with the generalized HDE was also established for the quintessence and for the Ricci DE model. In all the above cases, the effective equation of state (EoS) parameter corresponding to the holographic energy density was determined, by which the equivalence of various DE models with the respective generalized HDE models was further confirmed. The equivalent holographic cut-offs were determined by two ways: (1) in terms of the particle horizon and its derivatives, (2) in terms of the future horizon horizon and its derivatives.

The scalar field models of Tsallis holographic dark energy with Granda–Oliveros cutoff in modified gravity

This research explores the Tsallis holographic quintessence, k-essence, and tachyon models of dark energy in the modified f(R, T) gravity framework with Granda–Oliveros cutoff. We have analyzed the energy density through [Formula: see text]. 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 different values of Tsallis parameter δ in the region of ωΛ &gt; –1 for the EoS parameter. This correspondence allows reconstruction of the potentials and the dynamics for the scalar field models, if we set some constraints for the model parameters, which describe the accelerated expansion of the Universe.

Statefinder hierarchy model for the Barrow holographic dark energy

In this paper, we have used the state finder hierarchy for Barrow holographic dark energy (BHDE) model in the system of the FLRW Universe. We apply two DE diagnostic tools to determine ΛBHDE model to have various estimations of ▵. The first diagnostic tool is the state finder hierarchy in which we have studied S3(1)S4(1), S3(2)S4(2) and second is the composite null diagnostic (CND) in which the trajectories (S3(1)−ϵ), (S4(1)−ϵ), (S3(2)−ϵ)(S4(2)−ϵ) are discussed, where ϵ is fractional growth parameter. The infrared cut-off here is taken from the Hubble horizon. Finally, together with the growth rate of matter perturbation, we plot the state finder hierarchy that determines a composite null diagnosis that can differentiate emerging dark energy from ΛCDM. In addition, the combination of the hierarchy of the state finder and the fractional growth parameter has been shown to be a useful tool for diagnosing BHDE, particularly for breaking the degeneracy with different parameter values of the model.

Tachyon model of Tsallis holographic dark energy

In this paper, we consider the correspondence between the tachyon dark energy model and the Tsallis holographic dark energy scenario in an FRW universe.We demonstrate the Tsallis holographic description of tachyon dark energy in an FRW universe and reconstruct the potential and basic results of the dynamics of the scalar field which describe the tachyon cosmology. In a flat universe, in the tachyon model of Tsallis holographic dark energy, independent of the existence of interaction between dark energy and matter or not, \dot{T}^2 must always be zero. Therefore, the equation of state {\omega}_D is always -1 in such a flat universe. For a non-flat universe, \dot{T}^2 cannot be zero so that {\omega}_D=-1 which cannot be used to explain the origin of the cosmological constant. \dot{T}^2 monotonically decreases with the increase in \cos(R_h/a) and \cosh(R_h/a) for different {\delta}'s. In particular, for an open universe, \dot{T}^2 is always larger than zero, while for a closed universe, \dot{T}^2 is always smaller than zerowhich is physically invalid. In addition, we conclude that with the increase in \cos(R_h/a) and \cosh(R_h/a), \dot{T}^2 always decreases monotonically irrespective of the value of b^2.

Cosmological perturbations in the Tsallis holographic dark energy scenarios

We investigate the Tsallis holographic dark energy (THDE) models in the context of perturbations’ growth. We assume the description of dark energy by considering the holographic principle and the nonadditive entropy to carry out this. We implement the perturbed relativistic equations to achieve the growth of matter fluctuations, being the growth rate of the cosmic structures is non-negligible at low redshifts. To constrain and compare the models, we carry out the Bayesian analysis using the recent geometrical and growth rate observational data. The main results are: (i) the models are compatible with cosmological observations, (ii) the cosmological constant recovered with a $$1\sigma $$ confidence level, furthermore (iii) they could cross the phantom barrier. Finally, the models can relieve $$\approx 1\sigma $$ the $$\sigma _8$$ tension in the non-clustered case and can alleviate in $$\approx 2.8\sigma $$ the $$H_0$$ tension. From the model selection viewpoint, the data discarded the THDE models.