Holographic Dark Energy Model Research Articles

Some Bianchi Type Viscous Holographic Dark Energy Cosmological Models in the Brans–Dicke Theory

In this article, we analyze Bianchi type–II, VIII, and IX spatially homogeneous and anisotropic space-times in the background of the Brans–Dicke theory of gravity within the framework of viscous holographic dark energy. To solve the field equations, we have used the relation between the metric potentials as R = S n and the relation between the scalar field ϕ and the scale factor a as ϕ = a m . Also, we have discussed some of the dynamical parameters of the obtained models, such as the deceleration parameter q , the jerk parameter j , the EoS parameter ω v h d e , the density parameter Ω vhde , Om-diagnostic, squared speed of sound v s 2 , EoS plane ω v h d e − ω v h d e ′ , and statefinder plane r − s through graphical representation, which are significant in the discussion of cosmology. Furthermore, all the models obtained and graphically presented shown an expanding and accelerating Universe, which is in better agreement with the latest experimental data. The viscous holographic dark energy models are compatible with explaining the present cosmic accelerated expansion.

Rényi holographic dark energy models in teleparallel gravity

In this paper, we have investigated the physical behavior of cosmological models in the framework of modified teleparallel gravity. This model is established using a Rényi holographic dark energy (RHDE) model with a Hubble cut-off. Here, we have considered a homogeneous and isotropic Friedman universe filled with perfect fluid. The physical parameters are derived for the present model in compliances with 43 observational Hubble data sets. The equation-of-state parameter in terms of [Formula: see text] describes the transition of the universe between phantom and nonphantom phases in the context of [Formula: see text] gravity. Our model shows the violation of strong energy condition and the weak energy condition over the accelerated phantom regime. We also observed that these models occupy freezing regions through [Formula: see text]–[Formula: see text] plane. Consequently, our RHDE model is supported to the consequences of general relativity in the framework of [Formula: see text] modified gravity.

Barrow holographic dark energy model with GO cut-off - An alternative perspective

Recently, Barrow holographic dark energy (BHDE), based on Barrow entropy, has been proposed to describe the late acceleration of the universe. Contrary to the earlier analysis of this model in the literature, we consider the BHDE with the Granda–Oliveros length as IR cut-off, as a dynamical vacuum, having a constant equation of state [Formula: see text] We have analytically solved for the Hubble parameter and studied the evolution of cosmological parameters. The model is compared with the observational data on Hubble parameter (OHD36) and Supernovae type Ia (SN Ia), the pantheon data. In the absence of interaction between the dark sectors, we found that the model predicts a [Formula: see text]CDM-like evolution of the universe with an effective cosmological constant. In this case, the model is found to satisfy the generalized second law (GSL), irrespective of the value of the Barrow index. The interaction also shows the safe validity of GSL, for the extracted value of the Barrow index, [Formula: see text]. The thermodynamic analysis of the model predicts an end de Sitter phase of maximum entropy. We performed a dynamical system analysis, which reveals that the end de Sitter phase is stable. Furthermore, we performed the Information Criterion analysis using Akaike and Bayesian Information Criterion to compare the statistical compatibility of the present model with the standard [Formula: see text]CDM model.

Barrow holographic dark energy models in f(Q) symmetric teleparallel gravity with Lambert function distribution

The paper presents Barrow holographic dark energy (infrared cut-off is the Hubble horizon) suggested by Barrow [The area of a rough black hole, Phys. Lett. B 808 (2020) 135643] recently in an anisotropic Bianchi type-I Universe within the framework of [Formula: see text] symmetric teleparallel gravity, where the non-metricity scalar [Formula: see text] is responsible for the gravitational interaction. We consider two cases: Interacting and non-interacting models of pressureless dark matter and Barrow holographic dark energy by solving [Formula: see text] symmetric teleparallel field equations. To find the exact solutions of the field equations, we assume that the time-redshift relation follows a Lambert function distribution as [Formula: see text], where [Formula: see text], [Formula: see text] and [Formula: see text] are non-negative constants and [Formula: see text] represents the age of the Universe. Moreover, we discuss several cosmological parameters such as energy density, equation of state (EoS) and skewness parameters, squared sound speed, and [Formula: see text] plane. Finally, we found the values of the deceleration parameter (DP) for the Lambert function distribution as [Formula: see text] and [Formula: see text] which are consistent with recent observational data, i.e. DP evolves with cosmic time from initial deceleration to late-time acceleration.

Reconstructing extended f(P) cubic gravity from entropy-corrected holographic and new agegraphic dark energy models

This work deals with the newly approached extended [Formula: see text] cubic gravity in a cosmological background where [Formula: see text] denotes the cubic gravity. Here, we peruse the cosmological nature of the different types of dark energy candidates in the framework of [Formula: see text] gravity. Next, we study the reconstruction scenario of [Formula: see text] gravity model according to ordinary holographic dark energy, ordinary new agegraphic dark energy, entropy-corrected holographic dark energy in power-law and logarithmic versions and entropy-corrected new agegraphic dark energy in power-law and logarithmic versions with two classes of the scale factor. We derive different forms of the unknown function [Formula: see text] in the context of these dark energy candidates. By the trajectories of the EoS parameter [Formula: see text], all models give evidence of their candidature for the explanation of the phantom regime and also the quintessence regime in the late stage of the universe. Also, the stability condition ensures that our reconstructed models are classically stable.

Tsallis holographic dark energy model with event horizon cutoff in modified gravity

In this paper, we considered the Tsallis holographic dark energy model in frames of Nojiri–Odintsov gravity with [Formula: see text]. For IR, cutoff event horizon is taken. The cosmological evolution of such universe is investigated for various initial conditions and values of parameters. The dependence of the Hubble parameter [Formula: see text] from time in the future has an oscillation. It is shown that for [Formula: see text] appearance of singularities are typical and the time up to these singularities can be relatively small from cosmological viewpoint. The singularity is associated with the zero of second derivative of [Formula: see text] on [Formula: see text]. It is interesting to note that these models can describe observational data from Ia supernovae astrophysics and dependence of the Hubble parameter from redshift [Formula: see text] at least not worse than canonical [Formula: see text]CDM model.

Phase Space Analysis of Barrow Agegraphic Dark Energy

Using the Barrow entropy and considering the timescale as IR cutoff, a new holographic dark energy model named Barrow agegraphic dark energy (BADE) was proposed. We use phase space analysis method to discuss the evolution of the universe in three different mode of BADE (Q=0; Q=3αH(ρm+ρD); Q=H(αρm+βρD)). We find the attractor which represents the dark energy-dominated era exists in all cases. In the case Q=0 and Q=H(αρm+βρD) with β=0, the attractor can behave as the cosmological constant, and these models can used to mimic the cosmological constant.

Bianchi Type V Tsallis Holographic Dark Energy Model with Hybrid Expansion Law

A number of recent cosmological observations have provided increasing evidence that currently the universe is undergoing a phase of accelerated expansion, the root cause of which is supposed to be due to an exotic component of the universe with large negative pressure, dubbed dark energy. Out of the various candidates of dark energy proposed in the literature, the holographic dark energy emerged from the Holographic Principle is drawing much attention in the research field. In this paper, we investigate a spatially homogeneous and anisotropic Bianchi Type V space-time filled with non-interacting Tsallis holographic dark energy (THDE) with Hubble horizon as the IR cutoff and pressureless cold dark matter within the framework of General Relativity. Exact solutions of the Einstein field equations are obtained by considering the average scale factor to be a combination of a power law and an exponential law, the so called hybrid expansion law first proposed by Akarsu et al. (2014). We study the cosmological dynamics of various models for different values of the non-additive parameter that appeared in the Tsallis entropy and that for that appeared in the exponential function of the hybrid expansion law. We find that our model exhibits present cosmological scenario.

Holographic Description of the Dissipative Model of Universe with Curvature

We investigate the accelerated expansion of the late-time universe in the Friedmann-Robertson-Walker metric with nonzero curvature, applying a holographic principle based on a generalized holographic dark energy model introduced by Nojiri and Odintsov (2005,2006). We describe the evolution of the universe using a generalized equation of state in the presence of a viscous fluid. Solutions of the gravitational equation of motions are obtained in explicit form for a constant value of the thermodynamic parameter, and for various forms of the bulk viscosity. We calculate analytic expressions for infrared cut-offs in terms of the particle horizon, and derive the energy conservation law in the holographic picture. We show that the inclusion of nonzero curvature in the Friedmann equation leads to the appearance of additional singularities of type Big Rip in the Universe.

Running vacuum versus holographic dark energy: a cosmographic comparison

We perform a comparative study of different types of dynamical dark energy models (DDEs) using the cosmographic method. Among the models being examined herein we have the Running Vacuum models (RVMs), which have demonstrated considerable ability to fit the overall cosmological data at a level comparable to the standard cosmological model, Lambda CDM, and capable of alleviating the sigma _8 and H_0 tensions. At the same time we address a variety of Holographic dark energy models (HDEs) with different options for the time (redshift)-varying model parameter c=c(z). We deal with the HDEs under the double assumption of fixed and evolving holographic length scale and assess which one is better. Both types of DDEs (RVMs and HDEs) are confronted with the most robust cosmographic data available, namely the Pantheon sample of supernovae data (SnIa), the baryonic acoustic oscillations data (BAOs) extracted from measurement of the power spectrum and bispectrum of the BOSS data release, and the cosmic chronometer measurements of the Hubble rate (CCHs) at different redshifts obtained from spectroscopic observations of passively evolving galaxies. Using these data samples we assess the viability of the mentioned DDEs and compare them with the concordance Lambda CDM model. From our cosmographic analysis we conclude that the RVMs fare comparably well to the Lambda CDM, a fact which adds up more credit to their sound phenomenological status. In contrast, while some of the HDEs are favored using the current Hubble horizon as fixed holographic length, they become highly unfavoured in the more realistic case when the holographic length is dynamical and evolves as the Hubble horizon.

Marder space-time with Tsallis holographic dark energy

This present communication is an outcome of the investigation on newly proposed holographic dark energy model such as the Tsallis holographic dark energy (THDE) with Hubble horizon cutoff regarded as IR cutoff (infrared cutoff) for a spatially homogeneous and anisotropic Marder space-time in the framework of general relativity theory (GRT). Here, we have constructed the THDE models with Hubble horizon cutoff in three different ways, based on the following possibilities: (i) a varying deceleration parameter proposed by Mishra et al., (ii) hybrid expansion law (HEL) proposed by Akarsu et al. and (iii) a linearly varying deceleration parameter (LVDP) given by Akarsu and Dereli. The rapid expansion of the cosmos is thus justified for obtained models through the deceleration parameter (DP). In this way, the equation of state (EoS) parameter ([Formula: see text]) of the models describe the phantom and quintessence phases of the cosmos. Also, we compare the cosmological parameters of the obtained models with the parameters of [Formula: see text]CDM model, which indicates that the models-I and II are nearly identical to the [Formula: see text]CDM model.

Thermodynamics and stability analysis of Tsallis Holographic Dark Energy (THDE) models in [formula omitted] gravity

In this manuscript, we develop the counterpart of Tsallis holographic dark energy (THDE) model in F(R,T) theory (where R represents Ricci scalar and T is trace of energy momentum tensor (EMT)) using the two IR-cutoffs namely Hubble horizon (HH) and Granda-Oliveros (GO). The THDE is proposed on the basis of Tsallis entropy (Tsallis and Cirto, 2013) and the holographic hypothesis (Tavayef, 2018). Cosmic evolution is analyzed using the equation of state (EOS) parameter which results in both quintessence and phantom regimes. The stability analysis of reconstructed models is also made with the help of squared speed of sound. Moreover, we study the thermodynamic picture and developed constraints for the validity of generalized second law of thermodynamics (GSLT). It is remarked that these reconstructed models can be useful to further explore the cosmic issues.

Evolution of holographic dark energy model with adiabatic matter creation

We study the holographic dark energy (HDE) with adiabatic matter creation process to explain the present-day accelerated expansion of the Universe. The field equations are discussed and solved analytically for various cosmological parameters such as the Hubble parameter, deceleration parameter and effective equation of state parameter in terms of redshift by considering a more general form of the matter creation rate. The viability of such model is checked using the recent data of Type Ia supernovae Pantheon sample, Hubble function [Formula: see text] data, joined data of baryon acoustic oscillations/cosmic microwave background and latest local [Formula: see text] by SH0ES. We achieve the most fitting values of model parameters by performing the statistical analysis of our model with the three different combination of data sets. The HDE model, with IR cutoff as Hubble horizon, in the absence of matter creation does not show phase transition. While the induction of matter creation to the same model shows the recent transition from a decelerating to an accelerated phase. Our outcomes show that the model with matter creation is compatible with the data sets used. We find that the HDE model with matter creation provides the Hubble function which matches sufficiently well with the observed Hubble data. Finally, we perform geometrical and cosmographic analyses to explicate our model and compare it with the other dark energy models like [Formula: see text]CDM model. It is found that the evolution of model starts from Chaplygin gas region in early times, enters into quintessence region in medieval time and finally approaches to [Formula: see text]CDM model.

Inflationary epoch in the presence of holographic dark energy

We analyze the effects of the holographic dark energy model in a single field slow-roll inflation, taking into account both the holographic and the dark radiation components. In particular, we obtain the background evolution and compute the scalar and tensor power spectra. For the scalar sector we show that the power spectrum of the curvature perturbation encompasses the standard single field result and a correction proportional to Ωhde/ϵ, where Ωhde is the fractional density of the holographic component and ϵ is the first slow-roll parameter. This correction might be of order unity in the very beginning of the inflationary phase and decays rapidly. For the primordial gravitational waves we find the spectral index receives a correction from the graviton mass term, which decays in the first inflationary e-folds.

Kaniadakis holographic dark energy in Brans–Dicke cosmology

By using the holographic hypothesis and Kaniadakis generalized entropy, which is based on relativistic statistical theory and modified Boltzmann–Gibbs entropy, we build Kaniadakis holographic dark energy (DE) model in the Brans–Dicke framework. We derive cosmological parameters of the Kaniadakis holographic DE model, with IR cutoff as the Hubble horizon, in order to investigate its cosmological consequences. Our study shows that even in the absence of an interaction between the dark sectors of the cosmos, the Kaniadakis holographic dark energy model with the Hubble radius as IR cutoff can explain the present accelerated phase of the universe expansion in the Brans–Dicke theory. The stability of the model, using the squared of sound speed, has been checked and it is found that the model is unstable in non-interacting case and can be stable for some range of model parameters within the interacting case.

Cosmographic and thermodynamic analysis of Kaniadakis holographic dark energy

In this work, we study the cosmological implications of Kaniadakis holographic dark energy model in the context of Einstein and deformed Hořava-Lifshitz theories of gravity. We examine the various cosmological parameters to analyze the evolution of the universe. The Hubble parameter [Formula: see text] is discussed as it is evidence for accelerating universe and source to examine some other cosmological parameters. We probe coincidence parameter [Formula: see text] to check the matter- and energy-dominated eras of the universe. The deceleration parameter [Formula: see text] is explored for the expansion behavior of the universe while the jerk parameter [Formula: see text] is examined to compare the different dark energy models with [Formula: see text]CDM [Formula: see text] model. We examine the equation of state parameter [Formula: see text] to look into different phases of the universe. We calculate the perturbed parameter squared speed of sound [Formula: see text] to assess the stable behavior of the model. We also investigate the behavior of rate of change of entropy to discuss the validity of generalized second law of thermodynamics.

A Note on Varying G and Λ in Chern–Simons Modified Gravity

We have considered the holographic dark energy and modified holographic Ricci dark energy models to analyze the time-dependent gravitational constant G(t) and cosmological constant Λ(t) in the context of Chern–Simons modified gravity theory. The FRW metric is used to examine the physical and kinematical properties of these models, which predicted the accelerated expansion phase of universe. Further, the Λ(t) showed increasing trends while G(t) showed decreasing trends for both cases. Finally, the range −1.99×10−10yr−1≤G˙G≤0 was estimated mathematically, which is similar to the results obtained from observational data.

Corrected holographic dark energy with power-law entropy and Hubble Horizon cut-off in FRW Universe

In the present work, we investigate the power-law entropy corrected holographic dark energy (PLECHDE) model with Hubble horizon cutoff. We use 46 observational Hubble data points in the redshift range 0≤z≤2.36 to determine the present Hubble constant H0 and the model parameter n. It represents a phase transition of the universe from deceleration to acceleration and has the transition point at zt=0.71165. We investigate the observational constraints on the model and calculate some relevant cosmological parameters. We examine the model’s validity by drawing state-finder parameters that yield the result compatible with the modern observational data. The model’s physical and geometrical characteristics are also explored, and they are shown to match well with current observations of observational Hubble data (OHD) and the latest joint light curves(JLA) datasets.

Barrow holographic dark energy with Granda-Oliveros cutoff.

A study on the effects of implementing the Granda–Oliveros infrared cutoff in the recently introduced Barrow holographic dark energy model is presented, and its cosmological evolution is investigated. We find how the deformation parameter, Delta , affects the evolution of H(z) and that from this model it is possible to obtain an accelerated expansion regime of the universe at late times. We also observe that increasing Delta causes a transition of the EoS parameter from quintessence to phantom regimes. In addition, we show that the model can be used to describe the know eras of dominance. Finally, after studying the stability of the proposed model, a fit of the corresponding parameters is preformed, utilizing the measurements of the expansion rate of the universe, H(z). The best fit of the parameters is found to be (alpha ,, beta ,, Delta ) = left( 1.00^{+0.02}_{-0.02},,0.69^{+0.03}_{-0.02},,0.000^{+0.004}_{-0.000}right) at 1sigma C.L., for which the Bekenstein–Hawking relation is favored.

Barrow holographic dark energy in deformed Hořava–Lifshitz gravity

We discuss the cosmological implications of the interacting Barrow holographic dark energy model in the context of flat deformed Hořava–Lifshitz gravity by assuming the interaction ([Formula: see text]) between dark energy and pressureless dark matter. To understand the mechanism of recent accelerated expansion of the universe, we consider Hubble and event horizons as infrared cutoff. We investigate the evolutionary history of cosmological parameters especially the equation of state, Hubble, deceleration, squared speed of sound and find results that favor observational data of Planck 2018. It is found that the Hubble parameter lies in the range [Formula: see text] (for event horizon) and [Formula: see text] (for Hubble horizon). The equation of state parameter provides the phantom phase of the universe, while the deceleration parameter illustrates the accelerated phase of the universe. On the other hand, we plot the squared speed of sound and find the positive behavior which ensures the stability of underlying model. Moreover, we examine the generalized second law of thermodynamics of this cosmological system with barrow entropy as horizon entropy and observe that this law holds for both horizons.