Quintessence Dark Energy Models Research Articles

Dynamical system analysis of quintessence dark energy model

Our work deals with the dynamical system analysis of quintessence dark energy scalar field model with exponential potential. A dynamical system analysis has been applied at the background level. Using suitable transformation of variables, the evolution equations are reduced to an autonomous system for exponential form of the scalar potential. The critical points are analyzed with center manifold theory and stability has been discussed by using Schwarzian derivative. Finally, cosmological implications of the critical points are discussed and it is found that the stability of the late-time attractor changes for quintessence dark energy model.

LRS Bianchi type-I with Hubble’s horizon as IR cut-off in [formula omitted] gravity

we explored the holographic dark energy model using Hubble’s Horizon as the infrared (IR) cut-off in Locally Rotationally Symmetric (LRS) Bianchi type-I, considering the f(R) gravity framework in our analysis. In order to solve the field equations, we assume a relation F∝am and volumetric power law expansion (where m is constant). we have expressed various crucial cosmological parameters in terms of the redshift z and depicted them graphically to enhance our understanding of the expansion and evolution of the universe like holographic dark energy density (ρΛ), holographic dark energy pressure (pΛ), equation of state parameter (ω) , total energy density parameter (Ω) etc. Also, we analyzed the stability of the universe in our model through the squared speed of sound test and its validity by energy conditions. Ultimately, our model indicates that the universe is currently in an expanding phase, exhibiting an accelerating phase, closely approaching a flat geometry, and its behavior resembles that of a quintessence dark energy model.

Observational constraints on the wet dark fluid model in the fractal gravity

A flat Friedmann–Robertson–Walker (FRW) cosmological model with Wet Dark Fluid has been studied based on fractal gravity. The exact solution of the field equations is obtained using linear time-varying deceleration parameter (Akars̈u and Dereli, 2012) and assuming fractal parameter ξ≠0. The model parameters involved in the model have been constrained using the Hubble datasets H(z) of 77 data points, known as cosmic chronometers (CC), recently published Pantheon, and the joint data (CC+Pantheon samples). Additionally, we compare our model with ΛCDM in standard cosmology via error bar trajectories. We study the physical and the cosmographic parameters, such as the Hubble parameter H(z), deceleration parameter q(z), and the higher derivatives of the deceleration parameter q(z), etc. under cosmic observations. It is observed that our model transits from a decelerating state to an accelerating state at ztr≈2.764. The other astrophysical parameters such as the jerk parameter and snap parameter are also discussed. Finally, we conclude that our model is an accelerating quintessence dark energy model.

Dynamical analysis of a hyperbolic solution in scale-covariant theory

In this paper, we study an isotropic flat FLRW-model in scale-covariant theory of gravity [Formula: see text] 1 which is explained in terms of ordinary and covariant differentiation of scalar field [Formula: see text]. As we know, the deceleration parameter (DP) is time-dependent, so we consider the DP q as the function of t. Using this methodology, we find all the important cosmological factors in terms of a hyperbolic function of the cosmic time t. In turn, we create the model having the behavior of the late-time universe, which is ever accelerated expanding and faces a Big Freeze at the end. The model shows the quintessence dark energy model from early to late times. We compute the constrained values of Hubble parameter [Formula: see text] and the model parameter [Formula: see text] using joint analysis of the OHD data of 77-points and Pantheon bin data. The model exhibits point-type singularity as it begins with a point of zero volume, infinite energy density and temperature. Furthermore, we obtain the present value of DP [Formula: see text]. Also, we examine the ultimate behavior of our model by the proper analysis of energy conditions (ECs), cosmographical parameters and Statefinder diagnostic. Finally, the proposed model behaves like a quintessence dark energy model.

Bouncing and collapsing universes dual to late-time cosmological models

We use the Jordan frame–Einstein frame correspondence to explore dual universes with contrasting cosmological evolutions. We study the mapping between Einstein and Jordan frames where the Einstein frame universe describes the late-time evolution of the physical universe, which is driven by dark energy and non-relativistic matter. The Brans–Dicke theory of gravity is considered to be the dual scalar–tensor theory in the Jordan frame. We show that an Einstein frame universe, with cosmological evolution of the Λ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda $$\\end{document}CDM model, always corresponds to a bouncing Jordan frame universe governed by a Brans–Dicke theory. On the other hand, quintessence models of dark energy with non-relativistic matter component are shown to be always dual to a Brans–Dicke Jordan frame with a turn-around, i.e., a bounce or a collapse. The evolution of the equation of state of the quintessence field determines whether the turn-around is a bounce or a collapse. The point of the Jordan frame turn-around for all the cases can be tuned anywhere by choosing an appropriate Brans–Dicke parameter. This essentially leads to alternative descriptions of the late-time evolution of the physical universe, in terms of bouncing or collapsing Brans–Dicke universes in the Jordan frame. Therefore, the effect of dark energy can equivalently be seen as collapse of space in a conformally connected universe. We further study the stability of such conformal maps against linear perturbations. The effective bouncing and collapsing descriptions of the current accelerating universe may have interesting implications for the evolutions of perturbations and quantum fluctuations in the cosmological background.

Bianchi-I dark energy cosmological model in f(R,Lm)-gravity

We established an anisotropic Bianchi type-I dark energy model in this investigation’s [Formula: see text] gravity, where [Formula: see text] is an arbitrary function of the Ricci-scalar curvature [Formula: see text] and the matter Lagrangian [Formula: see text]. For the sake of our analysis, we have taken a particular form of this function, which is represented by the equation [Formula: see text], where [Formula: see text] are model free parameters, and [Formula: see text] is the “cosmological constant”. In order to derive the Hubble function [Formula: see text] in terms of redshift [Formula: see text], we analytically solved the field equations and established a connection between the energy parameters [Formula: see text] and [Formula: see text]. By using the [Formula: see text]-test, we compared this Hubble function to [Formula: see text] datasets to find the model and energy parameters that fit the data the best. Also, we have analyzed our result with statefinder and Om diagnostic analysis that suggests the model to be a quintessence dark energy model and tends to [Formula: see text]CDM model in late time.

Quintessence reconstruction through new Tsallis holographic dark energy model

In statistical theory, the Tsallis entropy is an extended form of the Boltzmann–Gibbs entropy. The dimensionless parameter [Formula: see text] is employed to state the quantitative difference from the standard scenario. The concepts of Tsallis entropy and the future event horizon are employed in formulating the present new Tsallis holographic dark energy (NTHDE) model. The model attempts to explain the properties of dark energy using the foundation of quantum gravity. The differential equation characterizing the evolution of the NTHDE density parameter is obtained. Expressions stating the dynamic behavior such as equation of state (EoS), deceleration and jerk parameters are obtained in terms of the NTHDE density parameter. For [Formula: see text], the quintessence nature of scalar field could completely characterize the NTHDE. A reconstruction of the scalar field’s dynamics and quintessence potential is attempted. We demonstrate that the diagnosis made by statefinder is adaptive enough to distinguish between quintessence and cosmological constant-based dark energy models. Additionally, observational data obtained from CC[Formula: see text] SNIa [Formula: see text] union 2.1 sources are used to evaluate the model’s effectiveness.

The dynamical analysis of a parameterized dark energy cosmological model in the f(R,G) gravity

In this paper, we investigate the dynamical behavior of the universe with a flat FLRW model in [Formula: see text] gravity, where [Formula: see text] and [Formula: see text] both signify the Ricci scalar and Gauss–Bonnet invariant. Furthermore, in order to determine the model’s behavior, it must have the late-time universe’s behavior, which involves both an accelerated expansion as well as ending in a big rip. We present a model that begins with a point-type singularity, i.e. a point with zero volume and infinite energy density, by using parametrization of the scale factor [Formula: see text]. The model’s actions are accelerating and expanding at the moment, and [Formula: see text]CDM in late times. Our extensive analysis encompasses the energy conditions, dynamics of certain model solutions and additional cosmological tests through a dominant model. Finally, the proposed framework acts exactly like a quintessence dark energy model in the current time and is reliable with standard cosmology [Formula: see text]CDM in late times.

Dark energy nature in logarithmic f(R,T) cosmology

This research paper is an investigation of dark energy nature of logarithmic [Formula: see text]-gravity cosmology in a flat FLRW space–time universe. We have derived modified Einstein’s field equations for the function [Formula: see text] where [Formula: see text] is the Ricci scalar curvature, [Formula: see text] is the trace of the stress energy momentum tensor, and [Formula: see text] is a model parameter. We have solved field equations in the form of two fluid scenarios as perfect fluid and dark fluid, where dark fluid term is derived in the form of perfect fluid source. We have made an observational constraint on the cosmological parameters [Formula: see text] and [Formula: see text] using [Formula: see text] test with observational datasets like Pantheon sample of SNe Ia and [Formula: see text]. With these constraints, we have discussed our model with deceleration parameter [Formula: see text], energy parameters [Formula: see text], EoS parameter [Formula: see text], etc. Also, we have done Om diagnostic analysis. The derived [Formula: see text] model shows a quintessence dark energy model [Formula: see text] and late-time universe approaches to [Formula: see text] CDM model.

A constrained cosmological model in [formula omitted] gravity

In this article, we study the expanding nature of the universe in the context of f(R,Lm) gravity theory, here R represents the Ricci scalar and Lm is the matter Lagrangian density. With a specific form of f(R,Lm), we obtain the field equations for flat FLRW metric. We parametrize the deceleration parameter in terms of the Hubble parameter and from here we find four free parameters, which are constraints and estimated by using H(z), Pantheon, and their joint data sets. Further, we investigate the evolution of the deceleration parameter which depicts a transition from the deceleration to acceleration phases of the universe. The evolutionary behaviour of energy density, pressure, and EoS parameter shows that the present model is an accelerated quintessence dark energy model. To compare our model with the ΛCDM model we use some of the diagnostic techniques. Thus, we find that our model in f(R,Lm) gravity supports the recent standard observational studies and delineates the late-time cosmic acceleration.

Transit string dark energy models in f(Q) gravity

In this paper, we have investigated an anisotropic cosmological model in [Formula: see text] gravity with string fluid in LRS Bianchi type-I universe. We have considered the arbitrary function [Formula: see text], where [Formula: see text] is model free parameter and [Formula: see text] is the cosmological constant. We have established a relationship between matter energy density parameter [Formula: see text] and dark energy density parameter [Formula: see text] through Hubble function using constant equation of state parameter [Formula: see text]. We have made observational constraint on the model using [Formula: see text]-test with observed Hubble datasets [Formula: see text] and SNe Ia datasets, and obtained the best fit values of cosmological parameters. We have used these best fit values in the result and discussion. We have discussed our result with cosmographic coefficients and found a transit phase dark energy model. Also, we analyzed the Om diagnostic function for anisotropic universe and found that our model is quintessence dark energy model.

Beyond dark energy Fisher forecasts: How the Dark Energy Spectroscopic Instrument will constrain LCDM and quintessence models

We baseline with current cosmological observations to forecast the power of the Dark Energy Spectroscopic Instrument (DESI) in two ways: (1) the gain in constraining power of parameter combinations in the standard $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model, and (2) the reconstruction of quintessence models of dark energy. For the former task we use a recently developed formalism to extract the leading parameter combinations constrained by different combinations of cosmological survey data. For the latter, we perform a nonparametric reconstruction of quintessence using the effective field theory of dark energy. Using mock DESI observations of the Hubble parameter, angular diameter distance, and growth rate, we find that DESI will provide significant improvements over current datasets on $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ and quintessence constraints. Including DESI mocks in our $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ analysis improves constraints on ${\mathrm{\ensuremath{\Omega}}}_{m}$, ${H}_{0}$, and ${\ensuremath{\sigma}}_{8}$ by a factor of two, where the improvement results almost entirely from the angular diameter distance and growth of structure measurements. Our quintessence reconstruction suggests that DESI will considerably improve constraints on a range of quintessence properties, such as the reconstructed potential, scalar field excursion, and the dark energy equation of state. The angular diameter distance measurements are particularly constraining in the presence of a non-$\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ signal in which the potential cannot be accounted for by shifts in ${H}_{0}$ and ${\mathrm{\ensuremath{\Omega}}}_{m}$.

Cosmic jerk parameter in symmetric teleparallel cosmology

In this paper, we have examined the recently proposed modified symmetric teleparallel gravity, in which gravitational Lagrangian is given by an arbitrary function of non-metricity scalar Q. We have considered a constant jerk parameter to express the Hubble rate. Moreover, we have used 31 points of OHD datasets and 1701 points of Pantheon+ datasets to constraint our model parameters by means of the Markov Chain Monte Carlo analysis. The mean values and the best fit obtained give a consistent Hubble rate and deceleration parameter compared to the observation values. In order to study the current accelerated expansion scenario of the Universe with the presence of the cosmological fluid as a perfect fluid, we have considered two forms of teleparallel gravity. We have studied the obtained field equations with the proposed forms of f(Q) models, specifically, linear $$f\left( Q\right) =\alpha Q+\beta $$ and nonlinear $$f\left( Q\right) =Q+mQ^{n}$$ models. Next, we have discussed the physical behavior of cosmological parameters such as energy density, pressure, EoS parameter, and deceleration parameter for both model. To ensure the validity of our proposed cosmological models, we have checked all energy conditions. The properties of these parameters confirm that our models describe the current acceleration of the expansion of the Universe. This result is also corroborated by the energy conditions criteria. Finally, the EoS parameter for both models indicates that the cosmological fluid behaves like a quintessence dark energy model.

Barrow entropic quintessence and dilation dark energy models with generalized HDE cut-off

In this work, we have analyzed the behaviors of extension of generalized Barrow holographic dark energy (BHDE). A “generalized BHDE model based on the particle and the future horizon using infrared cut-off” was proposed by [Nojiri et al. Phys. Lett. B 825, 136844 (2022)]. In this work, we have reviewed the generalized BHDE extension under the assumption of a generalized HDE cut-off. Using a scale factor of the form [Formula: see text], the dynamics of the cosmos have been discussed through graphic demonstration. By applying the “open-source emcee Python package”, the values of the free parameters [Formula: see text] and [Formula: see text] are estimated on 57 OHD points by the Markov chain Monte Carlo (MCMC) technique. We have examined the behavior of the equation of state (EoS) parameter, [Formula: see text] and dark energy density [Formula: see text]. We have also discussed the equivalence of holographic dark energy (DE) with the Barrow entropic DE and its extension. Also, we have explained quintessence and dilation DE models in the context of Barrow entropic DE.

Scalar field cosmology via Noether symmetries in energy–momentum squared gravity

This article examines the analytic solutions of isotropic spacetime with the minimal coupling of scalar field and matter in the context of energy–momentum squared gravity. The scalar field includes quintessence and phantom dark energy models. We evaluate solutions of a physical system through the Noether symmetry approach that provide some viable constraints to choose the cosmological models on the basis of current observations. We consider different models of this theory to establish Noether equations, symmetry generators and corresponding conserved quantities. We compute analytic solutions and examine their graphical representation for various cosmological quantities. The behavior of these quantities is found to be consistent with current observations implying that this theory shows expanding behavior of the universe. We find that symmetry generators and their conserved parameters exist in all cases. • Solutions of isotropic spacetime with minimal coupling of scalar field and matter are studied in modified theory. • We evaluate solutions of a physical system through the Noether symmetry approach. • The behavior of physical quantities is found to be consistent with current observations. • We find that symmetry generators and their conserved parameters exist in all cases.

Dynamics of a parametrized dark energy model in [formula omitted] gravity

We investigate a flat FLRW-model in f(R,T)-gravity, which includes the quadratic variation in scalar curvature R and the linear term of the trace of the stress–energy tensor T. In turn, we establish the model has the behaviour of the late time Universe, which is accelerated expanding. Using the parametrization of scale factor a(t), we propose a model, which begins with point-type singularity, i.e., the model starts with a point of zero volume, infinite energy density and infinite temperature. The model’s behaviour is accelerated expanding at present and ΛCDM in late times. Finally, the proposed model behaves like a quintessence dark energy model in the present time and is consistent with standard cosmology ΛCDM in late times.

The momentum constraint equation in parameterised post-Newtonian cosmology

Abstract We derive a theory-independent version of the momentum constraint equation for use in cosmology, as a part of the parameterised post-Newtonian cosmology framework. Our equations are constructed by adapting the corresponding quantities from formalisms constructed for testing and constraining gravity in isolated astrophysical systems, thereby extending the domain of applicability of these approaches up to cosmological scales. Our parameterised equations include both scalar and divergenceless-vector gravitational potentials, and can be applied to both conservative and non-conservative theories of gravity. They can also be used to describe the gravitational fields of both non-linear structures and super-horizon perturbations. We apply the parameterised equations we propose to quintessence models of dark energy, as well as scalar-tensor and vector-tensor theories of gravity. We find them to work well in each case. Our equations are highly compact, and are intended to be useful for constraining gravity in a theory-independent fashion in cosmology.

Cosmic birefringence and electroweak axion dark energy

Taking the recently reported non-zero rotation angle of the cosmic microwave background (CMB) linear polarization $\beta=0.35\pm0.14{\rm\, deg}$ as the hint for a pseudo Nambu-Goldstone boson quintessence dark energy (DE), we study the electroweak (EW) axion quintessence DE model where the axion mass is generated by the EW instantons. We find that the observed value of $\beta$ implies a non-trivial $U(1)$ electromagnetic anomaly coefficient ($c_{\gamma}$), once the current constraint on the DE equation of state is also taken into account. With the aid of the hypothetical high energy structure of the model inspired by the experimentally inferred $c_{\gamma}$, the model is shown to be able to make prediction for the current equation of state ($w_{\rm DE,0}$) of the quintessence DE. This is expected to make our scenario distinguishable in comparison with the cosmological constant ($w=-1$) and testable in future when the error in the future measurement of $w_{\rm DE,0}$ is reduced to $\mathcal{O}(1)\%$ level ($\delta w=\mathcal{O}(10^{-2})$).

On the occurrence of finite-time singularities in swampland-related quintessence dark energy models

In this work, we focus on the phase space singularities of interactive quintessence model in the presence of matter fluid. This model is related to swampland studies, that the outcomes affect all these swampland-related models with the same dynamical system. We shall form the dynamical system corresponding to the cosmological system, which is eventually autonomous, and by using the dominant balances technique we shall investigate the occurrence or not of finite-time singularities. Our results indicate that the dynamical system of the model may develop finite-time singularities, but these are not general singularities, like in the case that the matter fluids were absent, in which case singularities occurred for general initial conditions. Hence, the presence of matter fluids affects the dynamical system of the cosmological system, making the singularities to depend on the initial conditions, instead of occurring for general initial conditions.

Interacting dynamical dark energy with stable high-scale cosmological perturbations at radiation-dominated epoch

In this paper, the cosmological perturbations of dynamical dark energy and dark matter, which interact non-gravitationally are studied. This dark energy–dark matter non-gravitational interaction is linearly dependent on the energy densities of dark components. However, in the interacting quintessence dark energy models with such type of interaction, the non-adiabatic instabilities of cosmological perturbations at radiation-dominated epoch arise. To avoid this problem, the model of dynamical dark energy was chosen as the basis. Here, the equation of state parameter of dark energy evolves in time but can be assumed constant at early epoch, so this model can be tuned in such a way that the non-adiabatic instabilities would not appear. The drawback of this cosmological model is that the energy densities of dark components can take the negative values for the certain range of interaction parameter, so the conditions for positivity of dark components densities were derived. Using obtained constraints on the model parameters, the impact of coupling parameter on modification of cosmological perturbations’ evolution is analyzed.