Holographic Ricci Dark Energy Research Articles

Anisotropic Bianchi Type VI<sub>0</sub> Cosmological Models in a Modified <i>f</i>(<i>R,T</i>) Gravity

We investigate the spatially homogeneous and anisotropic Bianchi type VI0 cosmological models with modified Holographic Ricci Dark Energy subjected to f(R,T) gravity. We have obtained the solution of the field equations with the help of the power law relation among the scale factors. Dynamical parameters are calculated by using the connection between pressure and energy density. The kinematical implications of the models are also examined. Graphical presentation of different cosmological parameters is shown for distinct values of the parameter of the model

Generalized cutoff for late time acceleration and inflation: The cosmology of holographic fluid

Motivated by the work of Nojiri et al. [Phys. Lett. B 797 (2019) 134829], we utilize the holographic principle in the early universe to realize the holographic origin through inflation. A similar argument can be made for its well-researched late-time application, and the early-time horizon contraction naturally boosts holographic energy density at inflationary scales. After accounting for the IR cutoff adjustment and using holographic Ricci dark energy as the inflationary fluid, we have shown the significance of [Formula: see text] in the inflation realization. For holographic Ricci dark fluid’s potential to realize inflation, several restrictions were derived. The e-folding number was used to discuss inflationary observables and determine the slow-roll parameters. The study covered the effects of reconstructing the IR cutoff and the potential for inflation to be realized after taking into account holographic Ricci dark energy as a special instance of the most generalized Nojiri–Odintsov holographic dark energy [S. Nojiri and S. D. Odintsov, Gen. Relativ. Gravit. 38 (2006) 1285–1304]. Additionally, some time intervals for the potential of inflation have been calculated, and the behavior of the equation of state parameter has also been discussed.

Constraining the bounce realization with holographic background and analytical exploration of the consequences in a modified gravity framework

The work reported in this paper explores holographic bounce. In the first phase of the study, we chose a non-singular bouncing scale factor. Then we reconstructed [Formula: see text] gravity and analytically derived constraints on the bouncing parameter [Formula: see text]. These constraints helped us understand the scale factor’s quintessence or phantom behavior. Furthermore, we also explored the statefinder parameters for reconstructed [Formula: see text] and observed the attainment of [Formula: see text]CDM fixed point. Next, we considered the multiplicative bouncing scale factor inspired by S. D. Odintsov and V. K. Oikonomou Phys. Rev. D 94, (2016) 064022. For this choice, we discussed the types of singularities realizable for different cases. Through the Talyor series expansion, we analytically presented cases and subcases for different ranges of [Formula: see text] of the scale factor. In the last phase of the study, we demonstrated holographic bounce with the choice of the multiplicative scale factor. In this case, we considered holographic Ricci dark energy and Barrow holographic dark energy. We concluded that it is possible to generate constraints on the bouncing parameter for its feasibility for the EoS parameter. We concluded that the realization of holographic bounce is possible, and different suitable constraints can be derived for this multiplicative bouncing scale factor focusing on the realization of cosmic bounce.

An examination of the logotropic equation of state for Chaplygin gas and a generalized holographic model, as well as thermodynamic analysis utilizing scalar fields

This study proposes a method to reconstruct a generalized form of holographic dark energy and to analyse its cosmology, based on a logotropic equation of state. By assuming that the dark energy density is caused by holographic Ricci dark energy, one can calculate a scale factor for the universe’s overall energy density, provided by baryons, dark matter, and dark energy density. For the situation where the internal energy is in logarithmic form, the equation of state parameter is similarly obtained. In the following stage, a generalized Chaplygin gas is investigated using a logotropic equation of state, considering the scenario of a logarithmic internal energy. Modified generalized Chaplygin gas is also examined in the situation of logarithmic internal energy with logotropic equation of state, and related reconstruction is carried out. The generalized second law of thermodynamics is subsequently validated for event, particle, and Hubble horizons after taking into account the phantom and quintessence models using a logotropic technique.

A truncated scale factor to realize cosmological bounce under the purview of modified gravity

AbstractThe present paper reports a study on bounce realization with a truncated scale factor and the holographic fluid taken in the form of holographic Ricci Dark Energy, which is a particular case of holographic Nojiri–Odintsov model (Nojiri & Odintsov, 2006, Gen. Relativ. Gravit., 38(8), 1285). We have investigated the realization of bounce due to the application of a holographic fluid in the early scenario of the universe. We started with a de‐Sitter scale factor in our study and derived two modified forms using Taylor's series expansion. After studying the behavior of the resulting Hubble parameter, we identified as the suitable form of the scale factor to realize the bounce. It satisfied the conditions , , and before, at, and after the turn‐around point. We have also observed that the resulting equation of state (EoS) parameter violates the null energy condition required by the bounce realization. We have studied the bounce scenario in a modified gravity framework and derived the slow roll parameters. We have studied the behavior of the potential along with the slow‐roll parameters in this bouncing scenario.

Inhomogeneous equation of state and its consequences in a coupled fluid scenario and realization of Little Rip, Pseudo Rip and Bounce cosmology

Motivated by the work of P. H. Frampton et al. [Phys. Lett. B 708 (2012) 204; I. Brevik et al., Phys. Rev. D 84 (2011) 103508, arXiv:1107.4642 [hep-th]; I. Brevik et al., Phys. Rev. D 86 (2012) 063007, arXiv:1208.4770 [gr-qc]] this study reports on the reconstruction schemes for the inhomogeneous equation of state (EoS) first introduced by S. Nojiri et al., [Phys. Rev. D 72 (2005) 023003, arXiv:hep-th/0505215 [hep-th]] and the cosmology in the scenario of coupled fluid. We have considered the viscosity through the Eckart approach in an interacting system. The EoS parameter for the Little Rip, the [Formula: see text] in terms of cosmic time for Pseudo Rip, is reconstructed for the EoS for Bounce cosmology inhomogeneous viscous fluid. The EoS parameter is rebuilt for the coupled dark fluid in the nonviscous system for the Little Rip, Pseudo Rip and Bounce cosmology. The reconstructed EoS parameter for inhomogeneous viscous fluid was phantom for the Little Rip cosmology. The reconstructed EoS parameters of holographic Ricci dark energy (HRDE) of the coupled fluid in nonviscous systems are phantom for both the Little Rip and Pseudo Rip cosmology. The model HRDE of the coupled fluid in the nonviscous scenario for Pseudo-Rip cosmology indicates the possibility of singularity. The same model for the bounce cosmology violates the null energy condition and has the EoS parameter almost symmetric around the bouncing point.

Bianchi type II modified holographic Ricci dark energy model in Barber’s self-creation theory of gravitation

In this paper, we studied a spatially homogeneous and anisotropic Bianchi type II space-time in the presence of matter and modified holographic Ricci dark energy in Barber’s second self-creation theory of gravitation. We obtained exact solution of the field equations by assuming ( i) a special law of variation of the mean Hubble parameter and ( ii) the component [Formula: see text] of the shear tensor [Formula: see text] is proportional to the expansion scalar in the model. Some physical and dynamical parameters were determined and their significant roles are discussed with respect to cosmic evolution of the universe. We observe that the model is consistent with modern cosmological observational data.

Holographic Ricci DE as running vacuum with nonlinear interaction

The holographic Ricci dark energy (HRDE) can be treated as a running vacuum due to its analogy in the energy density, which is a combination of H and [Formula: see text], the model can predict either eternal acceleration or eternal deceleration. In the earlier works, we have shown that the presence of additive constant in the energy density or by considering possible interaction between dark sectors through a phenomenological term, the model can predict a transition from a prior decelerated to a late accelerated epoch. This paper analyzes the cosmic evolution of HRDE as running vacuum with a nonlinear interaction (NLI) between dark sectors in a flat Friedmann-Lemaitre-Robertson-Walker (FLRW) universe. We consider three possible NLI forms which give analytically feasible solutions. We have constrained the model using the Type1a Supernova(Pantheon) + CMB(Planck 2018) + BAO(SDSS) data and evaluated the best estimated values of all the model parameters. We have analyzed the evolution of the Hubble parameter and deceleration parameter of all three cases. We perform state finder analysis of the model, which implies the quintessence nature of the model and found that it is distinguishably different from the standard [Formula: see text]CDM model. The dynamical system analysis of all three cases confirms the evolution of the universe from an unstable prior matter-dominated era to a stable end de Sitter phase.

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.

Study of the effect of thermal radiation on singularities in presence of viscous holographic Ricci dark energy and modified Chaplygin gas

This work reports the effect of thermal radiation on singularities in the presence of holographic Ricci dark energy (HRDE) with generalized IR cut-off. The Eckart approach has been considered to initiate the study. The density of HRDE, which is a just particular cases of general Nojiri–Odintsov (NO) HDE [S. Nojiri and S. D. Odintsov, Unifying phantom inflation with late-time acceleration: Scalar phantom-non-phantom transition model and generalized holographic dark energy, Gen. Relativ. Gravit. 38(8) (2006) 1285–1304], in non-interacting and non-viscous case has been reconstructed and it is found that with the passage of cosmic time t, it is decreasing. The Equation of State (EoS) parameter of HRDE in non-interacting and viscous scenario, the EoS parameter of modified Chaplygin gas (MCG) in a non-interacting and non-viscous scenario and the EoS parameter of MCG in an interacting and non-viscous scenario have been reconstructed and studied. There is a chance of Type I, Type II, Type III, Type IV and [Formula: see text]-singularities for the conditions we obtained. For the effect of thermal radiation of inhomogeneous viscous fluid in an interacting scenario, there is a scope of avoidance of Big-Rip Singularity.

Viscous holographic f(Q) cosmology with some versions of holographic dark energy with generalized cut-offs

The work reported in this paper demonstrates the cosmology of f(Q) gravity and the reconstruction of various associated parameters with different versions of holographic dark energy with generalized cut-offs, where Q = 6 H 2. The Universe is considered to be filled with viscous fluid characterized by a viscous pressure Π = – 3 H ξ, where and H is the Hubble parameter. Considering the power law form of expansion, we have derived the expression of f(Q) under a non-viscous holographic framework and it is then extended to viscous cosmological settings with extended generalized holographic Ricci dark energy. The forms of f(Q) for both the cases are found to be monotonically increasing functions of Q. In the viscous holographic framework, f(Q) is reconstructed as a function of cosmic time t and is found to stay at a positive level with Nojiri-Odintsov cut-off. In these cosmological settings, the slow roll parameters are computed and a scope of exit from inflation and quasi-exponential expansion are found to be available. Finally, it is observed that warm inflationary expansion can be obtained from this model.

Anisotropic Bianchi type-II modified holographic Ricci dark energy model in scale-covariant theory of gravitation

In this paper, we obtain an anisotropic Bianchi type-II space–time with dark matter and modified holographic Ricci dark energy in the scale-covariant theory of gravitation. Exact solutions of the field equations are obtained by assuming (i) a negative constant value of the deceleration parameter, (ii) the component [Formula: see text] of the shear tensor [Formula: see text] is proportional to the mean Hubble parameter, and (iii) the gauge function [Formula: see text] is proportional to a power function of the average scale factor. We have also discussed some important physical aspects of the model, which is in agreement with the modern cosmological observations.

A Statistical Analysis of Observational Hubble Parameter Data to Discuss the Cosmology of Holographic Chaplygin Gas

A scheme for the generalized Chaplygin gas equation of state is shown by using the holographic Ricci dark energy. Regression analysis and a chi-square test were performed. A second order polynomial regression has been established as the relation between the Hubble Parameter and redshift. It has established a set of parameters that can predict the Equation of State (EoS) parameter.

Cosmic acceleration and stability of cosmological models in extended teleparallel gravity

In this paper, we study the model of f(T) gravity in the presence of dark matter and modified holographic Ricci dark energy (MHRDE) in locally rotationally symmetric (LRS) Bianchi type-I space–time. To achieve a physically realistic solution of the field equations, we have considered volumetric power and exponential expansion laws. We plot the corresponding cosmological parameters for dark energy components in terms of redshift; thereafter we investigate the accelerated expansion of the Universe. The physical and geometrical parameters of the models are also discussed in detail. The Statefinder diagnostic pair and jerk parameter are analysed to characterise completely different phases of the Universe.

Model for Modified Holographic Ricci Dark Energy in Gravitation Theory of Branc Dicke

In this cosmological model, we have studied the spatially homogeneous and anisotropic Bianchi type and axially symmetric model filled with dark matter and dark energy in Brans-Dicke’s [1] theory of gravitation. Here, we consider the modified holographic Ricci dark energy defined by Chen and Jing [21] as the suitable condition of dark energy. To obtain a solution we assumed the scale factor used Mishra et al. [43]. We have solved field equations of Brans-Dicke theory of gravitation with the help of an axially symmetric anisotropic Bianchi-type space-time. We have determined the cosmological parameters, namely, EoS parameter, MHRDE density, matter density, skewness parameter, and BD scalar field. Here the various phenomena like the expanding universe, and shift from anisotropy to isotropy are observed in this model. A detailed physical discussion of these dynamical parameters are presented graphically. Some physical and geometrical behaviours of the models are also discussed and found to be in good agreement with the recent observations (OHD+JLA) datasets.

Bayesian comparison of interacting modified holographic Ricci dark energy scenarios

We perform a Bayesian model selection analysis for interacting scenarios of dark matter and modified holographic Ricci dark energy (MHRDE) with linear interacting terms. We use a combination of some of the latest cosmological data such as type Ia supernovae, cosmic chronometers, the local value of the Hubble constant, baryon acoustic oscillations measurements and cosmic microwave background through the angular scale of the sound horizon at last scattering. We find moderate/strong evidence against all the MHRDE interacting scenarios studied with respect to Lambda CDM when the full joint analysis is considered.

Bayesian analysis of running holographic Ricci dark energy

ABSTRACT Holographic Ricci dark energy evolving through its interaction with dark matter is a natural choice for the running vacuum energy model. We have analysed the relative significance of two versions of this model in the light of type Ia supernovae (SN1a), the Cosmic Microwave Background (CMB), the Baryonic Acoustic Oscillations (BAO), and Hubble data sets using the method Bayesian inferences. The first one, model 1, is the running holographic Ricci dark energy (rhrde) having a constant additive term in its density form and the second is one, model 2, having no additive constant, instead the interaction of rhrde with dark matter (ΛCDM) is accounted through a phenomenological coupling term. The Bayes factor of these models in comparison with the standard Lambda cold dark matter have been obtained by calculating the likelihood of each model for four different data combinations, SNIa(307)+CMB+BAO, SNIa(307)+CMB+BAO+Hubble data, SNIa(580)+CMB+BAO, and SNIa(580)+CMB+BAO+Hubble data. Suitable flat priors for the model parameters has been assumed for calculating the likelihood in both cases. Our analysis shows that, according to the Jeffreys scale, the evidence for ΛCDM against both model 1 and model 2 is very strong as the Bayes factor of both models are much less than one for all the data combinations.

An interacting holographic dark energy model within an induced gravity brane

In this paper, we present a model for the late-time evolution of the universe where a dark energy-dark matter interaction is invoked. Dark energy is modeled through an holographic Ricci dark energy component. The model is embedded within an induced gravity braneworld model. For suitable choices of the interaction coupling, the big rip and little rip induced by the holographic Ricci dark energy, in a relativistic model and in an induced gravity braneworld model, are removed. In this scenario, the holographic dark energy will have a phantom like behavior even though the brane is asymptotically de Sitter.

Scrutinizing various phenomenological interactions in the context of holographic Ricci dark energy models

In this paper, we examine two types of interacting holographic dark energy model using Pantheon supernova data, BAO BOSS DR12, CMB Planck 2015, fgas (gas mass fraction) and SZ/Xray (Sunyaev–Zeldovich effect and X-ray emission) data from galaxy clusters (GC). In particular, we considered the Holographic Ricci dark energy and Extended holographic Ricci dark energy models. During this analysis, we considered seven types of phenomenological interaction terms (three linear and four non-linear) Q_1=3Hbleft( rho _{D}+rho _mright) , Q_2=3Hbrho _{D}, Q_3=3Hbrho _{m}, Q_4=3Hbleft( rho _{D}+frac{rho _{D}^2}{rho _{D}+rho _m}right) , Q_5=3Hbleft( rho _{m}+frac{rho _{m}^2}{rho _{D}+rho _m}right) , Q_6=3Hbleft( rho _{D}+rho _{m}+frac{rho _{D}^2}{rho _{D}+rho _m}right) , Q_7=3HbBig (rho _{D}+rho _{m}+frac{rho _{m}^2}{rho _{D}+rho _m}Big ) respectively. To find the best model we apply Bayesian Inference (BI) and use the Lambda CDM as the referring model for comparison. Using the Bayesian Evidence model selection method we note that the Q_3 and Q_5 interaction terms are favored by observational data among the other ones. The obtained results also demonstrated that the evidence from the Bayesian inference method against the considered types of holographic Ricci dark energy model is strong since the Lambda CDM is considered as the reference model and also the Lambda CDM is preferred over the models. We also observed that the values of the deceleration parameter and the transition redshift for all models are compatible with the latest observational data and Planck 2015. In addition, we studied the jerk parameter for all models. Using our modified CAMB code, we observed that the interacting models suppress the CMB spectrum at low multipoles and enhances the acoustic peaks.

Dynamics Of Frw Type Kaluza-Klein Mhrde Cosmological Model In Self-Creation Theory

ABSTRACT In this work, we have studied Friedmann–Robertson–Walker type Kaluza–Klein universe filled with pressureless matter and modified holographic Ricci dark energy in the frame work of Barber’s self-creation theory. While solving field equations we have considered hybrid expansion law of average scale factor. Also we have studied differences between open, flat and closed models. We have calculated some physical properties such as deceleration parameter(q), EoS parameter(ωde ), spatial volume(V ), expansion scalar(θ). The physical and geometrical aspects of the statefinder parameters(r, s) and ωde − ω ′ de plane are also discussed. In ω de− ω ′ de plane discussion we have observed that the flat model lies in freezing region and the closed model lies in thawing region. Also we have observed that for flat model ωde crosses the phantom divide line( i.e. ωde = -1) and shows quintom like behavior. Among the three models the flat model is in good agreement with recent observational data.