The superenergy of the universe is a tensorial quantity and it is a general relativistic analogue of the Appell's energy of acceleration in classical mechanics. We propose the measurement of this quantity by the observational parameters such as the Hubble parameter, the deceleration parameter, the jerk and the snap (kerk) known as statefinders. We show that the superenergy of gravity requires only the Hubble and deceleration parameter to be measured, while the superenergy of matter requires also the measurement of the higher-order characteristics of expansion: the jerk and the snap. In such a way, the superenergy becomes another parameter characterizing the evolution of the universe.
We investigate chameleonic Brans--Dicke model applied to the FRW universes. A framework to study stability and attractor solutions in the phase space is developed for the model. We show that depending on the matter field and stability conditions, it is possible to realize phantom-like behavior without introducing phantom filed in the model while the stability is fulfilled and phantom crossing occurs. The statefinder parameters to the model for different kinds of matter interacting with the chameleon scalar field are studied. We also compare our model with present day observations.
In this paper, we constrain four time-dependent dark energy (TDDE) models by using the Type Ia supernovae (SNe Ia), baryonic acoustic oscillations (BAO), observational Hubble parameter (OHD) data-sets as well as the single data point from the newest event GW150914. Subsequently, adopting the best fitting values of the model parameters, we apply the original statefinder, statefinder hierarchy, the growth rate of matter perturbations and $Om(z)$ diagnostics to distinguish the TDDE scenarios and the $Λ$CDM scenario from each other. We discover that all the TDDE models and $Λ$CDM model can be dist…
This article discusses a dark energy cosmological model in the standard theory of gravity - general relativity with a broad scalar field as a source. Exact solutions of Einstein's field equations are derived by considering a particular form of deceleration parameter $q$, which shows a smooth transition from decelerated to accelerated phase in the evolution of the universe. The external datasets such as Hubble ($H(z)$) datasets, Supernovae (SN) datasets, and Baryonic Acoustic Oscillation (BAO) datasets are used for constraining the model par parameters appearing in the functional form of $q$. T…
We link observational parameters such as the deceleration parameter, the jerk, the kerk (snap) and higher-order derivatives of the scale factor, called statefinders, to the conditions which allow to develop sudden future singularities of pressure with finite energy density. In this context, and within the framework of Friedmann cosmology, we also propose higher-order energy conditions which relate time derivatives of the energy density and pressure which may be useful in general relativity.
We present an autonomous phase-plane describing the evolution of field equations containing an agegraphic dark energy in 5D Brans- Dicke cosmology. To observationally verify the numerical results, we simultaneously solve the equations by constraining the model parameters with SNe Ia data. We find conditions for the existence and stability of the critical points (states of the universe) and numerically examine the cosmological parameters. We also investigate the model by means of statefinder diagnostic.
We study the possibility that the universe is subjected to a deformation, besides its expansion described by Friedmann's equations. The concept of smooth deformation of a riemannian manifolds associated with the extrinsic curvature is applied the standard FLRW cosmology. Starting from the resulting modified Friedman's equation we study two possible solutions with six models for each one in low redshift. In other to constrain the models, we calculate deceleration, jerk and Hubble parameters and compare with different data as the latest BAO/CMB + SNIa constraints, SNLS SNIa, x-ray galaxy cluster…
We focus on a series of $f(R)$ gravity theories in Palatini formalism to investigate the probabilities of producing the late-time acceleration for the flat Friedmann-Robertson-Walker (FRW) universe. We apply statefinder diagnostic to these cosmological models for chosen series of parameters to see if they distinguish from one another. The diagnostic involves the statefinder pair $\{r,s\}$, where $r$ is derived from the scale factor $a$ and its higher derivatives with respect to the cosmic time $t$, and $s$ is expressed by $r$ and the deceleration parameter $q$. In conclusion, we find that alth…
In this work, we explore the recently proposed new Tsallis agegraphic dark energy model in a flat FLRW Universe by taking the conformal time as IR cutoff with interaction. The deceleration parameter of the interacting new Tsallis agegraphic dark energy model provides the phase transition of the Universe from decelerated to accelerated phase. The EoS parameter of the model shows a rich behaviour as it can be quintessence-like or phantom-like depending on the interaction ($b^2$) and parameter $B$. The evolutionary trajectories of the statefinder parameters and $(ω_D, ω_D^{'})$ planes are plotted…
A new model of dark energy namely "ghost dark energy model" has recently been suggested to interpret the positive acceleration of cosmic expansion. The energy density of ghost dark energy is proportional to the hubble parameter. In this paper we perform the statefinder diagnostic tool for this model both in flat and non-flat universe. We discuss the dependency of the evolutionary trajectories in $s-r$ and $q-r$ planes on the interaction parameter between dark matter and dark energy as well as the spatial curvature parameter of the universe. Eventually, in the light of SNe+BAO+OHD+CMB observati…
In this paper, the holographic dark energy model with new infrared cut-off proposed by Granda and Oliveros has been investigated in spatially non flat universe. The dependency of the evolution of equation of state, deceleration parameter and cosmological evolution of Hubble parameter on the parameters of new HDE model are calculated. Also, the statefinder parameters $r$ and $s$ in this model are derived and the evolutionary trajectories in $s-r$ plane are plotted. We show that the evolutionary trajectories are dependent on the model parameters of new HDE model. Eventually, in the light of SNe+…
The coming few years are likely to witness a dramatic increase in high quality Sn data as current surveys add more high redshift supernovae to their inventory and as newer and deeper supernova experiments become operational. Given the current variety in dark energy models and the expected improvement in observational data, an accurate and versatile diagnostic of dark energy is the need of the hour. This paper examines the Statefinder diagnostic in the light of the proposed SNAP satellite which is expected to observe about 2000 supernovae per year. We show that the Statefinder is versatile enou…
The generalized Chaplygin gas (GCG) model in spatially flat universe is investigated. The cosmological consequences led by GCG model including the evolution of EoS parameter, deceleration parameter and dimensionless Hubble parameter are calculated. We show that the GCG model behaves as a general quintessence model. The GCG model can also represent the pressureless CDM model at the early time and cosmological constant model at the late time. The dependency of transition from decelerated expansion to accelerated expansion on the parameters of model is investigated. The statefinder parameters $r$…
We have analyzed the Barrow holographic dark energy (BHDE) in the framework of the flat FLRW Universe by considering the various estimations of Barrow exponent $\triangle$. Here we define BHDE, by applying the usual holographic principle at a cosmological system, for utilizing the Barrow entropy rather than the standard Bekenstein-Hawking. To understand the recent accelerated expansion of the universe, considering the Hubble horizon as the IR cut-off. The cosmological parameters, especially the density parameter ($Ω_{_D}$), the equation of the state parameter ($ω_{_D}$), energy density ($ρ_{_{…
In this work, we have studied the logarithmic entropy corrected holographic dark energy (LECHDE) model with Granda-Oliveros (G-O) IR cutoff. The evolution of dark energy (DE) density $Ω'_D$, the deceleration parameter, $q$, and equation of state parameter (EoS), $ω_Λ$, are calculated. We show that the phantom divide may be crossed by choosing proper model parameters, even in absence of any interaction between dark energy and dark matter. By studying the statefinder diagnostic and $ω_Λ-ω_Λ^{\prime}$ analysis, the pair parameters $\{r,s\}$ and $(ω_Λ-ω_Λ^{\prime})$ is calculated for flat GO-LECHD…
We study the dynamics of the scalar tensor cosmological model in the presence of tachyon field. In an alternative approach, in two exponential and power law form of the scalar field functions in the model, field equations are solved by simultaneously best fitting the model parameters with the most recent observational data. This approach gives us an observationally verified interpretation of the dynamics of the universe. We then discuss the best fitted of equation of state parameter, the statefinder parameters and the reconstructed scalar field in the model.
Quintessence Dynamics of Generalized Holographic Ricci Dark Energy in $f(\mathcal{T})$ Gravity: Stability, Phase-Space Attractor, and Statefinder Analysis
Indira Gandhi Kala Mahavidyalaya；G. S. Science, Arts and Commerce College；Sant Gadge Baba Amravati University
The illustration of cosmic acceleration under two interacting dark energy models (pilgrim dark energy with Granda and Oliveros cutoff and its generalized ghost version) in DGP braneworld framework is presented. In the current scenario, the equation of state parameter, deceleration parameter, $ω_{D}-ω'_{D}$ plane and statefinder diagnosis are investigated. The equation state parameter behave-like phantom era of the universe. The deceleration parameter depicts the accelerated expansion of the universe in both models. The cosmological planes like $ω_{D}-ω'_{D}$ and statefinder corresponds to $Λ$C…
In this paper, we have analyzed the significance of bulk viscosity in an axially symmetric Bianchi type-I model to study the accelerated expansion of the universe. We have considered four bulk viscosity parameterizations for the matter-dominated cosmological model. The function of the two significant Hubble $H(z)$ and deceleration parameters are discussed in detail. The energy parameters of the universe are computed using the most recent observational Hubble data (57 data points) in the redshift range $0.07 \leq z \leq 2.36)$. In this model, we obtained all feasible solutions with the viscous …
The present paper reports a study on the cosmological consequences arising from reconstructing $f(T)$ gravity through new holographic-polytropic dark energy. We assume two approaches, namely a particular form of Hubble parameter $H$ and a solution for $f(T)$. We obtain the deceleration parameter, effective equation of state as well as torsion equation of state parameters from total density and pressure in both cases. It is interesting to mention here that the deceleration and torsion equation of state represent transition from deceleration to acceleration phase. We study the statefinder parame…
In this article, the bulk viscosity is introduced in a modified gravity model. The gravitational action has a general $f(R,T)$ form, where $R$ and $ T $ are the curvature scalar and the trace of energy momentum tensor respectively. An effective equation of state (EoS) has been investigated in the cosmological evolution with bulk viscosity. In the present scenario, the Hubble parameter which has a scaling relation with the redshift can be obtained generically. The role of deceleration parameter $q$ and equation of state parameter $ω$ is discussed to explain the late-time accelerating expansion …
The newly released observational $H(z)$ data (OHD) is used to constrain $Λ(t)$CDM models as holographic and agegraphic dark energy. By the use of the length scale and time scale as the IR cut-off including Hubble horizon (HH), future event horizon (FEH), age of the universe (AU), and conformal time (CT), we achieve four different $Λ(t)$CDM models which can describe the present cosmological acceleration respectively. In order to get a comparison between such $Λ(t)$CDM models and standard $Λ$CDM model, we use the information criteria (IC), $Om(z)$ diagnostic, and statefinder diagnostic to measur…
In this work we explore under a holographic approach the dark energy - dark matter interaction in a non-flat Friedmann-Lemaitre-Robertson-Walker spacetime, with a cut-off for the dark energy component given in terms of the Hubble scale. Based on results coming from the use of observational data, we consider a positive interaction $Q$-term together with a Chevallier-Polarsky-Linder type parametrization for the coincidence parameter, we realize that the model admits a Type III future singularity, in this singular universe we have that for a null value of the curvature parameter its scale factor …
We look at observational constraints on the thawing class of scalar field models proposed to explain the late time acceleration of the universe. Using the recently introduced `Statefinder Hierarchy', we compare these thawing class of models with other widely studied dark energy (and modified gravity) models to check the underlying parameter degeneracies. We put constraints on the deviations of these thawing models from the canonical ΛCDM model using a large class of observational data, e.g, the Supernova Type Ia data, the BAO data, the CMB data and data from the measurements of the Hubble para…
The paper presents late time cosmology in $f(Q,T)$ gravity where the dark energy is purely geometric in nature. We start by employing a well motivated $f(Q,T)$ gravity model, $f(Q,T)=mQ^{n}+bT$ where $m,n$ and $b$ are model parameters. Additionally we also assume the universe to be dominated by pressure-less matter which yields a power law type scale factor of the form $% a(t)=c_{2}(At+c_{1})^{\frac{1}{A}}$, where $A=\dfrac{3(8π+b)}{n(16π+3b)% }$ and $c_{1}$ \& $c_{2}$ are just integration constants. To investigate the cosmological viability of the model, constraints on the model parameters we…
In this paper, we investigate the homogeneous and isotropic flat FLRW Universe in the logarithmic form of $f\left( Q\right) $ gravity, where $% Q $ is the non-metricity scalar, specifically, $f\left( Q\right) =α+β\log \left( Q\right) $, where $α$ and $β$ are free model parameters. In this study, we consider a parametrization of the Hubble parameter as $H\left( z\right) =η\left[ (z+1)^{-γ}+1\right] $, where $γ$ and $η$ are model/free parameters which are constrained by an $R^{2}$-test from 57 points of the Hubble datasets in the redshift range $0.07<z<2.36$. Further, we investigate the physical…
Observational constraints on viscous free-$γ$ fluid in $f(Q)$ gravity
Yukawa Institute for Theoretical Physics, Kyoto University（京都大学汤川理论物理研究所）；SR University（SR大学）；Birla Institute of Technology and Science, Pilani, Hyderabad Campus（比拉理工学院皮拉尼校区海得拉巴分校区）
In this paper, we study the interacting DGP braneworld Holographic Dark Energy model in a spatially flat FRW universe. Mainly, in this study we concentrate our attention on both interacting and non-interacting form of the model. The study shows that the equation of state and the deceleration parameter depict an accelerated universe for all variety of interactions. On the other hand, the StateFinder analysis shows that of the interacting and non-interacting behave similar to both quintessence and phantom dark energy and for the present value obey the behavior of quintessence. Moreover, the resu…
The subject of this paper is to investigate the weak regime covariant scalar-tensor-vector gravity (STVG) theory, known as the MOdified gravity (MOG) theory of gravity. First, we show that the MOG in the absence of scalar fields is converted into $Λ(t),G(t)$ models. Time evolution of the cosmological parameters for a family of viable models have been investigated. Numerical results with the cosmological data have been adjusted. We've introduced a model for dark energy (DE) density and cosmological constant which involves first order derivatives of Hubble parameter. To extend this model, correc…
We propose a new theoretical approach for a cosmological model, which starts from an exponential of the trace of the energy-momentum tensor-dependence on the gravitational action, to be summed to the Ricci scalar. We derive the referred field equations and Friedmann-like equations. We derive the scale factor, Hubble parameter and deceleration parameter, in terms of both time and redshift. In possession of those parameters in terms of the redshift, we confront their predictions with the observational Hubble dataset and the outcomes are pretty satisfactory so that the model can be seen as a new …
Homogeneous isotropic models with two torsion functions built in the framework of the Poincare gauge theory of gravity based on general expression of gravitational Lagrangian by certain restrictions on indefinite parameters are analyzed numerically. Special points of cosmological solutions at asymptotics and conditions of their stability in dependence of indefinite parameters are found. Procedure of numerical integration of the system of gravitational equations at asymptotics is considered. Numerical solution for accelerating Universe without dark energy and dark matter is obtained. It is show…
Cosmological Implications of the Gong-Zhang Parameterization in Rastall Gravity: A Deep Learning and Observational Study
GLA University（GLA大学）；United College of Engineering and Research（联合工程与研究学院）；IILM University（IILM大学）；Galgotias College of Engineering and Technology（加尔戈蒂亚工程技术学院）
In this paper, we try to consider the stability conditions of a modified gravity coupled by Weyl tensor. In this way, we indicate the suitable conditions for a successful bounce while the equation of state (EoS) parameter crosses the phantom divider for our new corrected modified gravity. In the spatially flat Friedmann-Lema\^ıtre-Robertson-Walker (FLRW) universe, according to the ordinary version of the holographic dark energy (HDE) model, describing accelerated expansion of the universe, will be considered. Our model's stability conditions and its general properties of attractors for scalar …
In this paper, we show that the expansion history of the Universe in power-law cosmology essentially depends on two crucial parameters, namely the Hubble constant $H_{0}$ and deceleration parameter $q$. We find the constraints on these parameters from the latest $H(z)$ and SNe Ia data. At 1$σ$ level the constraints from $H(z)$ data are obtained as $q=-0.18_{-0.12}^{+0.12}$ and $H_{0}=68.43_{-2.80}^{+2.84}$ km s$^{-1}$ Mpc$^{-1}$ while the constraints from the SNe Ia data read as $q=-0.38_{-0.05}^{+0.05}$ and $H_{0}=69.18_{-0.54}^{+0.55}$ km s$^{-1}$ Mpc$^{-1}$. We also perform the joint test u…
We have considered flat Friedmann-Robertson-Walker (FRW) model of the universe and reviewed the modified Chaplygin gas as the fluid source. Associated with the scalar field model, we have determined the Hubble parameter as a generating function in terms of the scalar field. Instead of hyperbolic function, we have taken Jacobi elliptic function and Abel function in the generating function and obtained modified Chaplygin-Jacobi gas (MCJG) and modified Chaplygin-Abel gas (MCAG) equation of states, respectively. Next, we have assumed that the universe filled in dark matter, radiation, and dark ene…
Einstein-Gauss-Bonnet (EGB) model is recently restudied in order to analyze new consequences in gravitation, modifying appropriately the Einstein-Hilbert action. The consequences in EGB cosmology are mainly geometric, with higher order values in the Hubble parameter. In this vein this paper is devoted to contribute with extra evidences about its pros and cons of the model from a cosmological point of view. We start constraining the characteristic parameter, $α$, of the EGB model when a cosmological constant as the catalyst for the acceleration is considered. The constrictions are developed at …
Reconstructions of $f(\mathcal{P})$ and $f(\mathcal{Q})$ gravity models from $(m,n)$-type Barrow Holographic Dark Energy: Analysis and Observational Constraints
This work is the reconstruction of the interaction rate of holographic dark energy whose infrared cut-off scale is set by the Hubble length. We have reconstructed the interaction rate between dark matter and the holographic dark energy for a specific parameterization of the effective equation of state parameter. We have obtained observational constraints on the model parameters using the latest Type Ia Supernova (SNIa), Baryon Acoustic Oscillations (BAO) and Cosmic Microwave Background (CMB) radiation datasets. We have found that for the present model, the interaction rate increases with expan…
We consider the interacting Tsallis Holographic Dark Energy (THDE), with the Granda-Oliveros (GO) scale as the infrared (IR) cutoff, as dynamical vacuum. We analytically solved for the Hubble parameter, in a spatially flat FLRW universe with dark energy and matter as components, and the solution traces the evolutionary path from the prior decelerated to the late accelerated epoch. Without interaction, the model predicts a $Λ$CDM like behavior with an effective cosmological constant. We used Pantheon Supernovae type Ia, observational Hubble data (OHD), cosmic microwave background (CMB), and bar…
In this work, we study a cosmological model of Bianchi type-I Universe in teleparallel gravity for a perfect fluid. To obtain the cosmological solution of the model, we assume that the deceleration parameter is a linear function of the Hubble parameter $H$ i.e. $q=-1+βH$ (where $β$ as a positive constant). Consequently, we get a model of our Universe, where it goes from the initial phase of deceleration to the current phase of acceleration. We have discussed some physical and geometric properties such as Hubble parameter, deceleration parameter, energy density, pressure, and equation of state …
Evolution of the bulk viscous matter dominated universe has been analysed using the full causal, Israel-Stewart theory for the evolution of bulk viscous pressure in the context of recent acceleration of the universe. The form of bulk viscosity is taken as $ξ=αρ^{1/2}. $ We obtained analytical solutions for the Hubble parameter and scale factor of the universe. The model parameters have been computed using the Type Ia supernovae observational data. The evolution of the prominent cosmological parameters were obtained. The age of the universe for the best estimated model parameters is found to be…
