Field Models Of Dark Energy Research Articles

Reconstruction of F(T,TG) gravity model with scalar fields

In this paper, we investigate the scalar field dark energy (DE) models within the context of [Formula: see text] gravity. Scalar field models are known for their dynamic nature. Parameters in the dynamical equation of state are responsible for the acceleration of the cosmos in recent epochs. We determined that the power-law cosmology fits the OHD and Pantheon data nicely. Using the Bayesian analysis and likelihood function in conjunction with the Markov Chain Monte Carlo (MCMC) method, we examine the three sets of the model parameters [Formula: see text] [Formula: see text] obtained by 57 points of the [Formula: see text] data, [Formula: see text] [Formula: see text] 1048 points of the Pantheon data and [Formula: see text] [Formula: see text] by using joint data ([Formula: see text]), respectively. We solved the modified Einstein’s field equations by taking the bulk-viscosity component [Formula: see text]. We also establish a correspondence between the [Formula: see text] gravity model and scalar field DE models such as quintessence, [Formula: see text]-essence, and DBI-essence. The nature of scalar fields and their corresponding potentials are being graphically analyzed. To check the validity of [Formula: see text] gravity model, we also analyze the behavior of energy conditions.

Observation constraints on scalar field cosmological model in anisotropic universe

In this study, we have explored a scalar field cosmological model in the axially symmetric Bianchi type-I universe. In this study, our aim is to constrain the scalar field dark energy model in an anisotropic background. For this purpose, the explicit solution of the developed field equations for the model is determined and analyzed. Constraints on the cosmological model parameters are established utilizing Markov Chain Monte Carlo (MCMC) analysis and using the latest observational datasets of OHD, BAO, and Pantheon. For the combined dataset (OHD, BAO, and Pantheon), the best-fit values of Hubble and density parameters are estimated as [Formula: see text], [Formula: see text] [Formula: see text] and [Formula: see text]. The model shows a flipping nature and redshift transition occurs at [Formula: see text], and the present value of decelerated parameter is computed to be [Formula: see text] for the combined dataset. We have explored characteristics like the universe’s age, particle horizon, deceleration parameter, and jerk parameter. The dynamical properties, such as energy density [Formula: see text], scalar field pressure [Formula: see text], and equation of state parameter [Formula: see text], are analyzed and presented. We have also described the behavior of the scalar potential [Formula: see text] and scalar field. Furthermore, the authors also described the behavior of energy conditions in scalar-tensor cosmology. The scenario of the present accelerated expansion of the universe is described by the contribution of the scalar field.

Viscous modified ghost scalar field dark energy Models with varying G

"We study QCD-modified scalar field models of dark energy, in the presence of both interaction and viscosity, with varying gravitational constant G. The equation of the state parameter of the interacting viscous QCD-modified ghost dark energy (MGDE) and the deceleration parameter of the universe, are derived. Furthermore, we establish the correspondence between the interacting viscous QCD-MGDE and scalar field models of the dark energy which includes quintessence, tachyon, k-essence, and dilaton energy density. This is done in the framework of a non-flat FRW universe. Hence we are able to establish a correspondence and reconstruct the potential V (ϕ) and dynamics ϕ of the scalar field models according to the evolution of viscous QCDMGDE."

A comprehensive parametrization approach for the Hubble parameter in scalar field dark energy models

This study proposes a novel parametrization approach for the dimensionless Hubble parameter i.e. E2(z)=A(z)+β(1+γB(z)) in the context of scalar field dark energy models. The parametrization is characterized by two functions, A(z) and B(z), carefully chosen to capture the behavior of the Hubble parameter at different redshifts. We explore the evolution of cosmological parameters, including the deceleration parameter, density parameter, and equation of state parameter. Observational data from Cosmic Chronometers (CC), Baryonic Acoustic Oscillations (BAO), and the Pantheon＋ datasets are analyzed using MCMC methodology to determine model parameters. The results are compared with the standard ΛCDM model using the Planck observations. Our approach provides a model-independent exploration of dark energy, contributing to a comprehensive understanding of late-time cosmic acceleration.

Cosmological singularities in non-canonical models of dark energy

The pursuit of unraveling the true essence of dark energy has become an immensely captivating endeavor in modern cosmology. Alongside the conventional cosmological constant approach, a diverse range of ideas has been proposed, encompassing scalar field-based models and various modified gravity approaches. A particularly intriguing notion involves exploring scalar field dark energy models within quantum gravitationally motivated cosmologies, with non-canonical theories standing out as a prominent candidate in this context. Hence, in this work, we investigate three widely recognized non-canonical scalar field dark energy models: phantom, quintom, and DBI dark energy models. By employing the Goriely–Hyde procedure, we demonstrate the presence of singularities in both finite and infinite time within these frameworks. and that these singularities can manifest regardless of the system’s initial conditions. Moreover, we further establish how cosmological singularities of types I-IV can arise in all of these models. The work goes to show that non-canonical regimes for dark energy can allow for most of the prominent cosmological singularities for a variety of models.

Observational constraints on a logarithmic scalar field dark energy model and black hole mass evolution in the Universe

We propose a logarithmic parametrization form of energy density for the scalar field dark energy in the framework of the standard theory of gravity, which supports the necessary transition from the decelerated to the accelerated behavior of the Universe. The model under consideration is constrained by available observational data, including cosmic chronometers data-sets (CC), Baryonic Acoustic Oscillation (BAO) data-sets, and Supernovae (SN) data-sets, consisting of only two parameters alpha and beta . The combined CC+BAO+SN data-sets yields a transition redshift of z_{tr}=0.79^{+0.02}_{-0.02}, where the model exhibits signature-flipping and is consistent with recent observations. For the combined data-sets, the present value of the deceleration parameter is calculated to be q_{0}=-0.43^{+0.06}_{-0.06}. Furthermore, the analysis yields constraints on both the parameter density value for matter and the present value of the Hubble parameter, with values of Omega _{m0}=0.25849^{+0.00026}_{-0.00025} and H_{0}=67.79_{-0.59}^{+0.59} km/s/Mpc, respectively, consistent with the results obtained from Planck 2018. Finally, the study investigates how the mass of a black hole evolves over time in a Universe with both matter and dark energy. It reveals that the black hole mass increases initially but stops increasing as dark energy dominates.

Conformally and disformally coupled vector field models of dark energy

Conformally and disformally coupled vector field models of dark energy

Reconstruction of f(R) Gravity from a Polytropic Gas Scalar Field Dark Energy Model

Reconstruction of f(R) Gravity from a Polytropic Gas Scalar Field Dark Energy Model

Interacting DBI essence in viscous [formula omitted] gravity for different choices of scale factor and thermodynamics with power-law and logarithmic entropy corrections

From the hydrodynamic viewpoint, the inclusion of viscosity in the theory of cosmic fluid may appear as an abstraction. Using modern observational results for the Hubble parameter and standard Friedmann formalism, we may have a description of the universe up to the inflationary era, or we may be able to analyse the probable ultimate fate of the universe. Inspired by this bulk viscosity formalism reviewed in Brevik et al., (2017) in this work, we report a study of the DBI essence scalar field model of dark energy (DE) interacting with pressureless dark matter (DM) in the presence of bulk viscous pressure of the form ξ=ξ0+ξ1H+ξ2(Ḣ+H2). We choose the scale factor in three forms: emergent, logamediate, and intermediate. We choose the interaction term Q in the form Q=3HδρΛ, where ρΛ denotes the density of the scalar field model of DE. We present a detailed cosmology of the interacting DE and observe a quintom behaviour of the equation of state (EoS). We conduct a statefinder analysis to attain ΛCDM fixed point by the interacting DE. Subsequently, we report a reconstruction scheme for f(T) gravity. Finally, we conduct thermodynamic analysis where we consider entropy’s logarithmic and power-law corrections.

Dynamical systems analysis of tachyon-dark-energy models from a new perspective

In this work we present a new scheme to study the tachyon dark energy model using dynamical systems analysis by considering parametrization of the equation of state(EoS) of the dark energy. Both the canonical and phantom field dynamics are investigated. In our method we do not require any explicit form of the tachyon potential. Instead of the potential we start with an approximate form of the EoS of the tachyon field. This EoS is phenomenologically motivated and contains some dimensionless parameters. Using our method we can construct the dynamical system which gives rise to the time evolution of the universe. We have considered two different parametrizations of the EoS and studied the phase space dynamics in details. Our analysis shows Taylor series parametrization of the EoS has serious cosmological limitations. Our proposal is generic in nature and can be applied to other scalar field dark energy models.

Probing Quintessence using BAO imprint on the cross-correlation of weak lensing and post-reionization H i 21 cm signal

ABSTRACT In this work, we investigate the possibility of constraining a thawing Quintessence scalar field model for dark energy. We propose using the imprint of baryon acoustic oscillation on the cross-correlation of post-reionization 21-cm signal and galaxy weak lensing convergence field to tomographically measure the angular diameter distance DA(z) and the Hubble parameter H(z). The projected errors in these quantities are then used to constrain the Quintessence model parameters. We find that independent 600 h radio interferometric observation at four observing frequencies 916, 650, 520, and 430 MHz with an SKA-1-Mid like radio telescope in cross-correlation with a deep weak lensing survey covering half the sky may measure the binned DA and H at a few per cent level of sensitivity. The Monte Carlo analysis for a power-law thawing Quientessence model gives the 1 − σ marginalized bounds on the initial slope λi, dark energy density parameter Ωϕ0 and the shape of the potential Γ at 8.63, 10.08, and $9.75{{\ \rm per\ cent}}$, respectively. The constraints improve to 7.66, 4.39, and $5.86{{\ \rm per\ cent}}$, respectively, when a joint analysis with supernovae and other probes is performed.

On finite time singularities in scalar field dark energy models based in the RS-II Braneworld

The quest of deciphering the true nature of dark energy has proven to be one of the most exciting in recent times in cosmology. Various ideas have been put forward in this regard besides the usual cosmological constant approach, ranging from scalar field based models like Quintessence and Phantom dark energy to various modified gravity approaches as well. A very interesting idea then is to consider scalar field dark energy models in quantum gravitationally corrected cosmologies with the RS-II Braneworld being one of the most well known in this regard. So in this work, we consider RS-II Braneworld based scalar field dark energy models and try to look out for the existence of finite time singularities in these regimes both through a dynamical system perspective, for which we employ the Goriely–Hyde singularity analysis method, and a physical perspective. Our approach is general in the sense that it is not limited to any particular class of potentials or for any constrained parameter region for the brane tension and is valid for both Quintessence and phantom dark energy regimes. We firstly show through Goriely–Hyde procedure that finite time singularities can exist in these models for a limited set of initial conditions and that this result would hold irrespective of any consideration given to the swampland dS conjecture. We then discuss the physical nature of the singularities that can occur in this regime, where we use a well motivated ansatz for the Hubble parameter and show that these models of dark energy can allow for weak singularities like those of Type III and Type IV and can also allow for strong singularities like the Big Rip (Type I).

REVERSE-ENGINEERED DBI-ESSENCE FIELD IN THE RAINBOW GRAVITY

The current astrophysical data sets have implied that our universe has recently entered in an accelerated expansion phase. In literature, it is commonly thought that the late-time speedy enlargement behaviour is caused by mysterious dark contents (dark matter, dark energy and dark radiation) that cannot be observed directly. Although Einstein's General Theory of Relativity has provided very successful theoretical explanations and predictions, it cannot explain the aforementioned unusual nature of the cosmos. This situation has led scientists to try to create a new theoretical model for the nature of dark contents. The cosmological constant, scalar fields, unified energy densities, additional dimension idea and modified gravity theories are among the prominent point of views. In this research, mainly, the reverse-engineering method is taken into account in the rainbow gravity formalism for the DBI-essence scalar field dark energy model. As it is known, scalar field models can be introduced with the help of some fundamental physics theories, but these theories do not provide a direct way to write explicitly the self-interaction potentials that we encounter in scalar field models. Therefore, the reverse-engineering method used in this research takes significant role while writing the self-interaction potential of a scalar field model.

Quintessence or phantom: Study of scalar field dark energy models through a general parametrization of the Hubble parameter

In this work we propose a simple general parametrization scheme of the Hubble parameter for the scalar field dark energy models. In our approach it is possible to incorporate both the quintessence and phantom scalar field in a single analytical scheme and write down relevant cosmological parameters which are independent of the nature of the scalar field. A general condition for the phantom barrier crossing has also been obtained. To test this approach, a well behaved parametrization of the normalized Hubble parameter has been considered and a wide variety of observational data like CMB data, Supernovae data, BAO data etc. has been used to constraint the various cosmological parameters. It has been found that data prefer the present value of the equation of state of the dark energy to be in the phantom domain. One interesting outcome of this analysis is that although the current value of the dark energy equation of state is phantom in nature, a phantom crossing of the EOS has taken place in the recent past. We have also carried out the Bayesian model comparison between ΛCDM model and the proposed model which indicates that this model is favored by data as compared to ΛCDM model.

Interacting Tsallis holographic dark energy and tachyon scalar field dark energy model in Bianchi type-II Universe

In this work, we study the interaction between the dark matter (DM) component and the dark energy (DE) component using the Tsallis holographic dark energy (THDE) density expression for a Bianchi type-II space–time within the framework of general relativity (GR). To obtain the exact solutions of Einstein’s field equations, we use two constraints: (i) the expansion scalar [Formula: see text] of the Universe is proportional to the component [Formula: see text] of the shear tensor [Formula: see text], i.e. [Formula: see text] and (ii) we assume that the scale factor follows the Hybrid Expansion Law (HEL). We have discussed some geometrical and physical parameters of our model such as the deceleration parameter (DP) and the equation of state (EoS) parameter. In these parameters, we plot their behavior in terms of redshift [Formula: see text]. We observe that the DP evolves from the early decelerating phase to the current accelerating phase with a current value consistent with the observation data. The EoS parameter evolves from a state of a stiff-matter fluid-dominated era [Formula: see text] for high redshift [Formula: see text] to a [Formula: see text]CDM era [Formula: see text] in the later times. Also, we have established a correspondence between the THDE model and the tachyon scalar field dark energy model. We have reconstructed the potential and the tachyon scalar field, which describes the current accelerated expansion of the Universe. Finally, using 51 values of observed Hubble measurement and the technique [Formula: see text]-test, we found the best fit value for the model parameters [Formula: see text], [Formula: see text] and [Formula: see text] (current value of the Hubble parameter). These results are consistent with the new measurements of [Formula: see text].37

Conformally and Disformally Coupled Vector Field Models of Dark Energy

Conformally and Disformally Coupled Vector Field Models of Dark Energy

Inflationary Dynamics of Tsallis Holographic Scalar Field Models in Chern-Simons Modified Gravity

The present study report reconstruction schemes for tachyon scalar field model of Dark Energy through Tsallis holographic dark fluid under the framework of Chern-Simons modified gravity. Emergent scale factor has been assumed. Reproducing the conservation equation for a coupled model with interaction term we have reconstructed the scalar field and the corresponding potential. The reconstructed energy density have been plotted for the case. Evolutionary behaviour of potential for the case have been pictorially presented.

Dynamics of tachyon dark energy on large scales and its imprint on the observed galaxy power spectrum

In the present work, we study the large scale matter power spectrum as well as the observed galaxy power spectrum for a noncanonical tachyon field dark energy model considering the full general relativistic perturbation equations. We form a set of coupled autonomous equations, including both the background and linearly perturbed quantities, and obtain their solutions numerically with proper set of initial conditions. We consider different scalar field potentials for our study. Deviations from the concordance $\mathrm{\ensuremath{\Lambda}}$ cold dark matter ($\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$) model are studied for different relevant quantities. Our study shows that the noncanonical tachyon dark energy model produces enhanced gravitational potentials and comoving density contrast, as well as linear growth factor for matter perturbations compared to $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$. It is also observed that, for tachyon dark energy models, there is suppression of power on large scales compared to both the $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model as well as previously studied canonical scalar field models.

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 generalized anisotropic scalar field models

This paper is devoted to investigate the interacting generalized ghost pilgrim dark energy model in the background of anisotropic universe in general relativity. We analyze the two parameters i.e., hubble parameter and equation of state parameter to explore the cosmological evolution of the Bianchi type universe. We study scalar field dark energy models i.e., quintessence, dilaton, K-essence and tachyon to check the consistency of the current universe with their scalar field and corresponding potentials. Further, we check the compatibility of fractional density of matter and dark energy with recent observations of Plank along with their graphical analysis. It is remarkable to conclude that that both fractional densities admits consistency with Plank data 2018 in all cases of Bainchi type universe.