Ghost Dark Energy Model Research Articles

Generalized ghost dark energy model in extended modified theory of symmetric teleparallel gravity

Generalized ghost dark energy model in extended modified theory of symmetric teleparallel gravity

Analysis of cosmic evolution admitting Garcia-Salcedo ghost and generalized ghost dark energy models

This study aims to explore the Garcia-Salcedo ghost dark energy and generalized ghost dark energy models in the context of f(R,T2) theory, where R is the Ricci scalar and T2 is the self-contraction of stress–energy tensor. We investigate the non-interacting case only corresponding to flat Friedmann–Robertson–Walker universe. We reconstruct the corresponding f(R,T2) gravity models using the considered dark energy models by taking two particular models of this gravity. The stability analysis is performed for all the cases. The behavior of the equation of state parameter is also checked. It is found that some of the reconstructed f(R,T2) models successfully describe both the phantom and quintessence epochs of the universe, which support the current cosmic accelerated expansion. This exploration reveals the intricate connections between dark energy models and modified gravitational theory, providing significant understanding into the dynamics of the cosmos on a large scale.

Ghost dark energy in Tsallis and Barrow cosmology

According to the thermodynamics-gravity conjecture, any modification to the entropy expression leads to the modified cosmological field equations. Based on this, we investigate the cosmological consequences of the modified Friedmann equations when the entropy associated with the horizon is in the form of Tsallis/Barrow entropy and the dark energy (DE) component is in the form of ghost dark energy (GDE). We perform a dynamical system analysis and see that the Tsallis GDE(TGDE) and Barrow GDE(BGDE) can exhibit a correct phase space evolution for suitable range of the free parameters(0<Δ<1 for BGDE and β<3/2 for TGDE). We find that in BGDE and TGDE (with Q=3b2H(ρD+ρm)), there exist an early radiation dominated phase of expansion which is absent for GDE model in standard cosmology. It is worth mentioning that seeking an unstable phase of matter dominated in TGDE leads to a new constraint on β (<3/2). Using the resulting range of free parameters from latter step we find that both models are capable to explain the cosmic evolution from deceleration to an accelerated phase. We observe that increasing Δ (β) parameters leads to a delay in the cosmic phase transition. We conclude that BGDE and TGDE are viable cosmological models which predict a consistent phase transition of the cosmic expansion for suitable ranges of the parameters. We also calculate the squared sound speed for both models and find out that they are unstable against perturbations. Next, we proceed the statefinder analysis and see that both models are significantly distinct from ΛCDM as well as with respect to each other at past epochs, while both of them catch the standard cosmology at far future. We also explore the impacts of the non-extensive parameters on the density perturbations and find out that the pattern of density contrast (δ) evolution in TGDE/BGDE is distinct from GDE in standard cosmology.

Analysis of reconstructed modified [formula omitted] gravity

This paper studies the reconstruction criterion in the framework of f(Q,T) gravity using a ghost dark energy model, where Q represents the non-metricity and T is the trace of energy–momentum tensor. In this regard, the correspondence scenario for a non-interacting scheme is used to construct the ghost dark energy f(Q,T) model. We consider the flat Friedmann–Robertson–Walker universe with a power-law scale factor and pressure-less matter. We investigate the behavior of the equation of state parameter and examine the stability of the ghost dark energy model via the squared speed of sound parameter. The equation of state parameter depicts the phantom era, while the squared speed of sound reveals a stable ghost dark energy model for the entire cosmic evolutionary paradigm. Finally, we study the cosmography of the ωGDE−ωGDE′ and r−s planes that correspond to a freezing region and Chaplygin gas model, respectively. It is concluded that the reconstructed ghost dark energy model represents the evolution of the cosmos for suitable choices of the parametric values.

Generalized ghost dark energy model in Brans–Dicke theory with logarithmic scalar field

We study generalized ghost dark energy model in Brans–Dicke theory within the framework of flat Friedmann–Lemaitre–Robertson–Walker Universe. We assume the well-motivated logarithmic form of Brans–Dicke scalar field in terms of the scale factor to find the observational parameters such as equation of state parameter [Formula: see text] and deceleration parameter q. It is observed that the equation of state parameter crosses the phantom divide line [Formula: see text] for a suitable range of model parameters. We observe that the deceleration parameter is time-dependent which shows the recent phase transition from decelerated to accelerated expansion of the Universe. Moreover, the model shows that the Universe will go through two future phase transitions, recent accelerated expansion to decelerated expansion and again decelerated expansion to accelerated expansion. We have also plotted the trajectories of the model in the [Formula: see text] plane for different values of parameters and explored the freezing and thawing regions. Further, we apply the sound squared speed method to check the stability of the model and found that the model is stable for suitable range of parameters.

Study of dark energy models in [formula omitted] theory

This paper investigates the quantum chromodynamics ghost model of dark energy in the framework of f(R,T2) theory. The investigation centers on the non-interacting ghost dark energy model in a Friedmann–Robertson–Walker universe. Various cosmic parameters such as the Hubble parameter, equation of state and deceleration parameter are computed to examine the implications of the ghost dark energy model. Further, it is discovered that the equation of state parameter of ghost dark energy traverses the phantom regime. The stability analysis of this model is conducted using the squared sound speed. This study serves to reconstruct the model of gravity by incorporating dark matter and the ghost dark energy model. Special emphasis is placed on the scenario where the function is defined as f(R,T2)=f1(R)+f2(T2). In this context, our attention is focused on a specific model that allows for the use of the standard continuity equation in this modified theory. The conclusion drawn is that the reconstructed ghost dark energy model in the framework of f(R,T2) gravity exhibit phantom or quintessence eras of the cosmos, describing the accelerated expansion of the universe. This exploration sheds light on the complex interplay between quantum chromodynamics, dark energy and modified theories of gravity, offering valuable insights into the dynamics of the cosmos at large scales.

Sign-changeable interacting ghost dark energy model versus the cosmic age

In this paper, we discuss cosmic age problem in the case of ghost dark energy (GDE) model. To this end, we use two observational data sets to constrain the free parameter space of the models. Next, we try to set new limits on the mentioned free parameter space using the age of the universe. In this work, both of these tasks are done for the GDE model in the presence of the sign-changeable interaction terms. To this end, three classes of interaction terms are considered that provide a sign-changeability possibility. For one of these cases, the age problem passes completely and there is no new bound of free parameters. For two others the age test sets some constrains on the models. In addition to cosmic age problem, we investigate some other properties of these three models including ability to cross the phantom line, accelerating phase of cosmic expansion and the stability against cosmic perturbations.

Cosmic age problem in holographic and ghost dark energy models

ABSTRACT In this paper, we study the cosmic age problem in holographic (HDE) and generalized ghost dark energy (GGDE) models. To this end, we consider these two models in presence of non-linear interaction terms for three special cases, presented in the literature. We explain the impacts of the mentioned interaction terms on the cosmic age during the evolution of the Universe. There are many old cosmic objects (OCOs) which their evaluated age is not consistent with that of dark energy models. Here, we confine our attention on five cases of more known OCOs at different redshift. The purpose is to constrain the DE models, using the age of these OCOs. We obtain boundary values for free parameters of the HDE (b2 and c) using the age test and find that, such non-linear interactions can alleviate the age problem in spite of the linear one. The GGDE was already constrained using a joint analysis of data sets SHBC. We find a new bound for ξ that wasn’t predicted via SHBC analysis. Beside, we find that the GGDE can completely alleviate the cosmic age problem.

Cosmographic approach to Running Vacuum dark energy models: New constraints using BAOs and Hubble diagrams at higher redshifts

Abstract In this work we study different types of dark energy (DE) models in the framework of the cosmographic approach, with emphasis on the Running Vacuum models (RVMs). We assess their viability using different information criteria and compare them with the so-called Ghost DE models (GDEs) as well as with the concordance ΛCDM model. We use the Hubble diagrams for Pantheon SnIa, quasars (QSOs), gamma-ray bursts (GRBs) as well as the data on baryonic acoustic oscillations (BAOs) in four different combinations. Upon minimizing the χ2 function of the distance modulus in the context of the Markov Chain Monte Carlo method (MCMC), we put constraints on the current values of the standard cosmographic parameters in a model-independent way. It turns out that, in the absence of BAOs data, the various DE models generally exhibit cosmographic tensions with the observations at the highest redshifts (namely with the QSOs and GRBs data). However, if we include the robust observations from BAOs to our cosmographic sample, the ΛCDM and RVMs are clearly favored against the GDEs. Finally, judging from the perspective of the deviance information criterion (DIC), which enables us to compare models making use of the Markov chains of the MCMC method, we conclude that the RVMs are the preferred kind of DE models. We find it remarkable that these models, which had been previously shown to be capable of alleviating the σ8 and H0 tensions, appear now also as the most successful ones at the level of the cosmographic analysis.

Ghost scalar field dark energy models from an extended Kaluza–Klein perspective

Reconstruction process of scalar field models (quintessence, tachyon, dilaton and K-essence), which can be performed by making use of some dark energy density definitions such as holographic, Ricci, new agegraphic and ghost types proposals, has been an interesting and very attractive area to many physicists in literature. In this work, in a five-dimensional framework, we establish a correspondence between the quintessence, tachyon and the dilaton type scalar field definitions and the generalized ghost dark energy model by considering the extended form of the Kaluza–Klein (EKK) gravity. Accordingly, we numerically study the associated equation of state parameters, as well as their kinetic energy and scalar potential terms.

Interacting Anisotropic Ghost Dark Energy Model in $$\boldsymbol{f(R,T)}$$ Theory of Gravity

We seek the cosmological outcome of a ghost dark energy (GDE) model with sign-changeable interaction in $$f(R,T)$$ modified theory of gravity. We assume that the universe is filled with two fluid, a barotropic fluid, and ghost dark energy. With the particular choice of the functional $$f(R,T)=R+2f(T)$$ , where $$R$$ is the Ricci scalar and $$T$$ is the trace of the stress-energy tensor, we obtain exact solutions of the model by using the energy density of generalized GDE and a law of variation for the Hubble parameter $$H$$ . Interestingly, at late times, the equation of state (EoS) parameter in our model corresponds to a phantom dark energy model showing consistency with the recent observational data. A study of the statefinder parameters demonstrates that our model corresponds to the $$\Lambda$$ CDM model at certain time. A correspondence between GDE and Phantom DE is established. The phantom dynamics of the potential and the scalar field is reconstructed, which illustrates the accelerated phase of the Universe. The physical and geometric properties of the model are discussed.

Study of anisotropy effects on QCD ghost dark energy using the cosmological data

We investigate the effects of anisotropy on ghost dark energy model from the latest observational data. We have fitted our model with the present observational data including Supernovae type Ia (SNIa) and the Hubble expansion history H(z) datasets, and compare the results with the $\Lambda $CDM model. We test the possible dipole anisotropy of the ghost dark energy model, by using the Pantheon and the Supernova Legacy Survey (SNLS) sample. We also examine the behavior of different cosmological parameters such as Hubble parameter, equation of state (EoS) parameter and deceleration parameter of ghost dark energy model in an anisotropic universe. With the help of best fit results, we find that the EoS parameter represents quintessence era while a transition in the expansion history of universe from a deceleration phase to an accelerated one around $z\approx 1.42$ with the $1\sigma '$ confidence level. Finally we found that the presence of anisotropy improved the fit to observations with respect to that provided by an isotropic dark energy model.

Ghost dark energy model in the presence of a linear, sign-changeable interaction

در مطالعه ی حاضر به بررسی مدل گوست انرژی تاریک تعمیم یافته در حضور یک عبارت برهم کنشی خطی باعلامت متغیر پرداخته می­شود. با محاسبه­ی پارامترهای تحولی و رسم نمودارها ملاحظه می­شود که مدل در ابتدا انبساط کندشونده و در نهایت انبساط تند شونده را بیانگر است که از تطابق خوبی با مشاهدات برخوردار می­باشد. از طرفی رفتار مدل به ازای تغییر پارامترهای b و xi مورد بررسی قرار می­گیرد. در نهایت با بیان دو راهکار به تحلیل کامل­تری از مدل پرداخته می­شود. تحلیل اول بررسی پایداری مدل از طریق مجذور سرعت صوت است که با افزایش پارامتر ،می­تواند افزایش یافته و به مقادیرمثبت که نشان از پایداری دارد، برسد. در تحلیل دوم به بررسی پارامترهای پرداخته می­شود و نمودارهای q -r-s و r رسم می­شوند که در نمودار ، تفاوت هایی نسبت به مدل انرژی تاریک گوست معمولی یافته می­شود. از نمودارها می­توان دید که این مدل مقدار {r=1,s=0} را در زمان­های اخیر تجربه خواهد کرد

Cosmic evolution of ghost dark energy models in f(G,T) gravity

The aim of this paper is to study the reconstruction paradigm for both ghost as well as generalized ghost dark energy models in the context of [Formula: see text] gravity. To accomplish this, we use correspondence scenario for pressureless flat FRW universe with power-law scale factor. The cosmological behavior of reconstructed models is analyzed through graphical analysis of deceleration, equation of state, squared speed of sound parameters and phase planes. It is found that the deceleration parameter represents accelerated epoch for both models whereas equation of state parameter indicates phantom era of the universe for ghost dark energy model and quintessence for its generalized version. The phase planes [Formula: see text] and [Formula: see text] indicate the freezing region with phantom phase for both reconstructed dark energy models. We conclude that the squared speed of sound parameter leads to the stability of generalized ghost dark energy model only.

Bianchi type-III, V and VI0 generalized ghost dark energy models with polytropic gas in Brans-Dicke theory of gravitation

This paper elaborates the homogeneous and anisotropic Bianchi type-III, V and VI0 space times filled with matter and generalized ghost dark energy components in the framework of Brans-Dicke (Phys. Rev. 124, 925 1961) theory of gravitation. The behavior of generalized ghost dark energy for Bianchi type-III, V and VI0 background is discussed. The solutions of the field equations obtained using following two assumptions: (i) shear scalar of the model is proportional expansion scalar, which leads to a relation between the metric, (ii) scalar field in the Brans-Dicke theory is a function of average scale factor of the models. We have further established a correspondence between the generalized ghost dark energy models with the polytropic gas dark energy model. We also reconstructed the potential and dynamics of the scalar field. We discuss some physical and geometrical properties of the obtained models which are found to be consistent with recent observation.

Study of QCD generalized ghost dark energy in FRW universe

A phenomenological generalized ghost dark energy model has been studied under the framework of FRW universe. In ghost dark energy model the energy density depends linearly on Hubble parameter (H) but in this dark energy model, the energy density contains a the sub-leading term which is depends on mathcal {O} (H^2), so the energy density takes the form rho _D=alpha H+ beta H^2, where alpha and beta are the constants. The solutions of the Friedman equation of our model leads to a stable universe. We have fitted our model with the present observational data including Stern data set. With the help of best fit results we find the adiabatic sound speed remains positive throughout the cosmic evolution, that claims the stability of the model. The flipping of the signature of deceleration parameter at the value of scale factor a=0.5 indicates that the universe is at the stage of acceleration i.e. de Sitter phase of the universe at late time. Our model shows that the acceleration of the universe begin at redshift z_{ace}approx 0.617 and the model is also consistent with the current observational data.

Ghost dark energy in the deformed Hořava–Lifshitz cosmology

We study the cosmological consequences of the ghost models of dark energy (DE) in the framework of Hořava–Lifshitz gravity. We calculate the equation-of-state parameter, the deceleration parameter, the classical stability and the dimensionless density parameter of the models in both noninteracting and interacting scenarios. We find that, for some values of the parameter, this model can admit a transition from the deceleration phase to the accelerated phase around [Formula: see text], while at the late time ([Formula: see text]) we have [Formula: see text] meaning that this model mimics a cosmological constant. We find that in the setup of Hořava–Lifshitz gravity, ghost dark energy (GDE) models are classically unstable. We observe that unlike the generalized ghost dark energy (GGDE), the ghost dark energy cannot provide proper behavior for all the cosmological parameters simultaneously, with the same values of the models’ couplings.

Cosmography of Generalized Ghost Dark Energy Model in f(G) Gravity

This paper is devoted to construction of generalized ghost dark energy f(G) model by using correspondence scheme for both interacting and noninteracting scenarios with pressureless matter and power-law scale factor. We study the cosmological implications of the resulting model through equation of state parameter and ωDE – $$\omega _{{DE}}^{'}$$ as well as r – s plane. We also discuss stability of the resulting model through squared speed of sound parameter. The equation of state parameter represents phantom phase of the Universe for both cases while the squared speed of sound indicates stability of this model. The ωDE – $$\omega _{{DE}}^{'}$$ plane represents thawing region whereas r – s plane corresponds to phantom and quintessence DE regimes for both interacting and noninteracting cases.

Ghost dark energy model in f(G) gravity

In this paper, we investigate cosmological consequences of ghost dark energy model in modified Gauss-Bonnet gravity. We construct ghost dark energy f(G) model by using correspondence scenario for both interacting and non-interacting schemes. For this purpose, we consider FRW universe with pressureless matter and power-law scale factor. We examine the behavior of equation of state parameter and check the stability of ghost dark energy model through squared speed of sound parameter. We also analyze the behavior of phase planes like ωeff−ωeff′ and r−s graphically. It is found that the equation of state parameter represents quintessence era for non-interacting while phantom phase of the universe for interacting case. The squared speed of sound indicates stable ghost dark energy model for both cases. The ωeff−ωeff′ plane shows thawing region for non-interacting while freezing region for interacting case. The r−s plane corresponds to Chaplygin gas model in both scenarios. We conclude that ghost dark energy model describes evolution of the universe for appropriate choice of parameters.

Anisotropic behavior of dark energy models in fractal cosmology

We study effects of anisotropy (although low) on the ghost and generalized ghost dark energy (DE) models in the framework of fractal cosmology. We obtain the equation of state parameter, [Formula: see text], the deceleration parameter, and the evolution equation of the ghost and generalized ghost dark energy. We find that, in both models, [Formula: see text] cannot cross the phantom line and eventually the universe approaches a de-Sitter phase of expansion. We show that the anisotropy effects on ghost and generalized ghost dark energy (GDE) in fractal cosmology correspond to [Formula: see text]CDM limit on the statefinder plane. We evaluate the anisotropy effects on both the linear perturbation and the spherical collapse from the DE models and compare them with the results of the DE of the Friedmann–Robertson–Walker and [Formula: see text]CDM models. We also show that in ghost and generalized ghost cosmologies, the growth factor [Formula: see text] rise front the values for an [Formula: see text]CDM universe. Finally, we constrain the model parameters by using the maximum likelihood analysis and a combined dataset of baryon acoustic oscillation (BAO) and OHD.