Behavior Of Dark Energy Research Articles

Research on Conjecture of Dark Energy

An in-depth exploration of the origin of dark energy is undertaken. Dark energy is a fascinating and mysterious concept within the realm of astrophysics. It was discovered through a series of astronomical observations and theoretical studies. For instance, the observation of distant supernovae revealed the accelerating expansion of the universe, leading to the postulation of an unknown forcedark energy. The crucial role played by dark energy in the universe is then delved into. It is now widely accepted that dark energy is responsible for accelerating the expansion of the universe. This has significant implications for the understanding of the cosmos and its ultimate fate. Next, the relationship between other matter in relation to celestial bodies and dark energy is examined. Black holes and dark matter are two important components of the universe that have a complex interaction with dark energy. Having immense gravitational pulls, black holes and dark matter, which is believed to make up a large portion of the total matter in the universe, both influence the distribution and behavior of dark energy. The current inferences about dark energy and some famous hypotheses put forward by renowned scientists are also discussed. These hypotheses range from modifications of general relativity to the existence of extra dimensions and new forms of matter. Finally, personal thoughts and speculations on the relationship between dark energy and the higher-dimensional universe are offered. The idea of a higher-dimensional universe has intrigued scientists for decades, and there is growing interest in exploring whether dark energy could be related to these hidden dimensions. This could potentially open up new avenues for understanding the fundamental nature of the universe and its mysteries

Dark energy reconstructions combining baryonic acoustic oscillation data with galaxy clusters and intermediate-redshift catalogs

Cosmological parameters and dark energy (DE) behavior are generally constrained assuming a priori models. We work out a model-independent reconstruction to bind the key cosmological quantities and the DE evolution. Through the model-independent Bézier interpolation method, we reconstructed the Hubble rate from the observational Hubble data and derived analytic expressions for the distances of galaxy clusters, type Ia supernovae, and uncorrelated baryonic acoustic oscillation (BAO) data. In view of the discrepancy between Sloan Digital Sky Survey (SDSS) and Dark Energy Spectroscopic Instrument (DESI) BAO data, they were kept separate in two distinct analyses. Correlated BAO data were employed to break the baryonic--dark matter degeneracy. All these interpolations enable us to single out and reconstruct the DE behavior with the redshift $z$ in a totally model-independent way. In both analyses, with SDSS-BAO or DESI-BAO datasets, the constraints agree at a $1$--sigma confidence level (CL) with the flat Lambda CDM model. The Hubble constant tension appears solved in favor of the Planck satellite value. The reconstructed DE behavior exhibits deviations at small $z$ ($>1$--sigma CL), but agrees ($<1$--sigma CL) with the cosmological constant paradigm at larger $z$. Our method hints at a slowly evolving DE, consistent with a cosmological constant at early times.

Non-flat Friedmann-Lemaitre-Robertson-Walker universe with Barrow holographic dark energy

In this paper, we study a non-flat Friedmann-Lemaitre-Robertson-Walker (FLRW) universe filled with cold dark matter and Barrow holographic dark energy. We assume the Hubble horizon as IR cutoff and the scale factor to obey a hybrid expansion law to construct a cosmological model within the framework of General Relativity. The physical and geometrical properties of the model are discussed by studying the evolution of various parameters of cosmological importance. The behaviour of the dark energy equation of state parameter wDE is also studied for both interacting and non-interacting Barrow holographic dark energy. We observe that the Barrow exponent ∆ significantly affects the dark energy equation of state parameter which in turn exhibits the behaviour of quintessence and phantom dark energy. The evolution of the jerk parameter is also studied.

Cosmic analysis through dark energy models in fractal universe with non-linear interaction term

This study investigates the cosmological effects of different dark energy models within a fractal universe framework, including a non-nonlinear coupling between dark components. We examine well-known dark energy models, including generalized ghost and power-law entropy corrected, using the Hubble horizon as the infrared boundary. Well-known cosmological parameters are also analyzed to explain the current scenario of the universe. Hence, to find the universe’s expansion rate, we evaluate the Hubble parameter (H), the deceleration parameter (q) to investigate its acceleration or deceleration, the equation of state parameter ωΛ to check the nature of dark energy and Vs2 to study the stability of cosmic evolution. The behavior of ωΛ−ωΛ′ plane is also investigate as it is a valuable tool in cosmology for tracking the evolutionary behavior of dark energy and understanding its dynamic properties over time. Our analysis reveals that the Hubble parameter ranges from 74.5−1.5+1.5 and the generalized ghost dark energy model to 77−3+3 for the power-law entropy corrected model. Both models demonstrate the phase transition of the universe from deceleration to acceleration phase and ωΛ→−1, indicating a cosmological constant-like behavior. Stability of the models is assessed using the squared speed of sound parameter, confirming stability across all cases. Furthermore, the results for the ωΛ−ωΛ′ plane are consistent with Planck 2018 for both models.

Evolution of the Universe with quintessence model in Rastall gravity

Abstract We investigate the Universe’s evolution within the framework of Rastall gravity, which is an extension of the standard ΛCDM model. Utilizing a linear parametrization of the Equation of State (EoS) in a Friedmann-Lemaître-Robertson-Walker (FLRW) background, we constrain the model parameters through analysis of cosmic chronometers (CC), Pantheon, Gold, Gamma Ray Burst (GRB), and Baryon Acoustic Oscillations (BAO) datasets, as well as their joint analysis, under 1σ and 2σ confidence levels, considering the Rastall parameter λ. The constrained parameters are then used to compare our model with the standard ΛCDM model. Our findings include a detailed examination of the model’s physical interpretations and demonstrate the potential for an accelerating universe expansion in later times, aligning with the observed behavior of dark energy.

Reconsidering bulk viscosity in Brans–Dicke theory

In this paper, we reconsider the concept of bulk viscosity in Brans–Dicke theory to study accelerated expansion of the universe in a flat Friedmann–Robertson–Walker metric. In recent works on bulk viscosity in Brans–Dicke theory, the power-law form of Brans–Dicke scalar field has been taken to explain recent phase transition of the universe, however, power-law form confronts constant deceleration parameter problem. Therefore, we consider recently proposed well-motivated logarithmic form of Brans–Dicke scalar field to discuss bulk viscous model in Brans–Dicke theory. We obtain the values of deceleration parameter and equation of state parameter for the model, and plot their graphs against the redshift parameter z. The plots show that the model is able to explain the recent phase transition of the universe and equation of state parameter shows the behavior of dark energy. Further, we apply two important analysis, namely, [Formula: see text] analysis and thermodynamic analysis to examine our model. The [Formula: see text] analysis shows that our model belong to thawing region and shows similarities with quintessence model. All the trajectories start from the point [Formula: see text] with different negative values of w having quintessence behavior. The thermodynamic analysis shows that the model satisfies generalized second law of thermodynamics.

Exploring Mathematical Models of Dark Energy: A Comprehensive Literature Review

The elusive nature of dark energy, driving the accelerated expansion of the universe, remains one of the most profound mysteries in modern cosmology. In this literature review, we undertake a comprehensive examination of the mathematical models proposed to elucidate the properties and behavior of dark energy. Beginning with an overview of the observational evidence for dark energy, we delve into the diverse array of theoretical frameworks developed to describe this enigmatic phenomenon. Through a critical analysis of peer-reviewed literature, observational data, and theoretical constructs, we explore the strengths, limitations, and implications of various mathematical descriptions of dark energy. Our review encompasses both phenomenological parametrizations and fundamental physics-based models, providing insights into the intricacies of dark energy dynamics. By synthesizing the current state of knowledge, we aim to contribute to the ongoing discourse surrounding dark energy and its implications for our understanding of the universe. This review serves as a valuable resource for researchers and enthusiasts alike, fostering further inquiry and advancement in the captivating field of cosmology

Cosmological evolution of new Tsallis agegraphic dark energy with conformal time as IR-cutoff

This paper considers the only sectors to constitute the present universe as the dark matter and dark energy. The proposed new agegraphic dark energy model studies the gradual transition from matter to dark energy in sequential order, including the current dominance of the matter sector by dark energy. The model utilizes concepts of Tsallis entropy and the Karolyhazy relation with conformal time [Formula: see text] as the time scale. Various evolutionary aspects of the universe are characterized by Tsallis parameter [Formula: see text] and the model constant [Formula: see text]. Expressions for dynamic behavior of dark energy, as a differential equation, equation of state and deceleration parameters are obtained to describe the thermal history of universe evolution. Also, the stability of the model is analyzed through squared sound speed parameter. The analysis is made by considering an interaction as well as independence among the constituent sectors of the universe.

Gravitational wave probes of Barrow cosmology with LISA standard sirens

We study the Barrow cosmological model, which proposes that quantum gravity effects create a complex, fractal structure for the universe's apparent horizon. We leverage the thermodynamics-gravity conjecture. By applying the Clausius relation to the apparent horizon of the Friedmann-Lemaître-Robertson-Walker universe within this framework, we derive modified field equations where the Barrow entropy is linked to the horizon. We assess the Barrow cosmology against current observations — cosmic microwave background, supernovae, and baryon acoustic oscillations data — and include projections for future Laser Interferometer Space Antenna (LISA) standard sirens (SS). Our numerical results suggest a modest improvement in the Hubble tension for Barrow cosmology with phantom dark energy behavior, compared to the standard cosmological model. Furthermore, incorporating simulated LISA SS data alongside existing observational constraints tightens the limitations on cosmological parameters, particularly the deformation exponent.

Dynamical Dark Energy in Light of Cosmic Distance Measurements. II. A Study Using Current Observations

Abstract We extract key information on dark energy from current observations of BAO, OHD and H 0, and find hints of dynamical behavior of dark energy. In particular, a dynamical dark energy model whose equation of state crosses −1 is favored by observations. We also find that the Universe has started accelerating at a lower redshift than expected.

Bianchi type-III THDE quintessence model with hybrid scale factor

The current research investigates the behavior of the Tsallis holographic dark energy (THDE) model with quintessence in a homogeneous and anisotropic Bianchi type-III space–time. We construct the model by using two conditions: ( i) expansion scalar ( θ) is proportionate to shear scalar ( σ) in the model and ( ii) hybrid scale factor a = t βe γt, where β > 0 and γ > 0 are constants. Our study is based on Type Ia supernovae data in combination with CMB and BAO observations (Giostri et al., JCAP 3, 27); the present values of Hubble constant and deceleration parameter are H0 = 73.8 and q0 = −0.54, respectively. Compiling our theoretical models with these data, we obtain [Formula: see text] for [Formula: see text], respectively. We completed an entirely novel form of cosmic model where the expansion occurs during the present accelerated phase for the constraints. We have discussed the conformity among the scalar field model of quintessence and THDE model. To understand the Universe, we have also established the relations for distance modulus, luminosity distance, and angular-diameter distance. Some geometric and physical aspects of the THDE model are also highlighted.

Quintessence like behavior of symmetric teleparallel dark energy: Linear and nonlinear model

In Einstein’s General Relativity (GR), the gravitational interactions are described by the spacetime curvature. Recently, other alternative geometric formulations and representations of GR have emerged in which the gravitational interactions are described by the so-called torsion or non-metricity. Here, we consider the recently proposed modified symmetric teleparallel theory of gravity or [Formula: see text] gravity, where [Formula: see text] represents the non-metricity scalar. In this paper, motivated by several papers in the literature, we assume the power-law form of the function [Formula: see text] as [Formula: see text] (where [Formula: see text], [Formula: see text], and [Formula: see text] are free model parameters) that contains two models: Linear ([Formula: see text]) and nonlinear ([Formula: see text]). Further, to add constraints to the field equations we assume the deceleration parameter form as a divergence-free parametrization. Then, we discuss the behavior of various cosmographic and cosmological parameters such as the jerk, snap, lerk, [Formula: see text] diagnostic, cosmic energy density, isotropic pressure, and equation of state (EoS) parameter with a check of the violation of the strong energy condition (SEC) to obtain the acceleration phase of the Universe. Hence, we conclude that our cosmological [Formula: see text] models behave like quintessence dark energy (DE).

THDE models with specific cutoffs and correspondence with quintessence field

In this paper, we investigated the general behaviors of the Tsallic holographic dark energy (THDE) model in general relativity. Here, we take the Bianchi [Formula: see text] metric, which is homogeneous and anisotropic. We investigate the THDE models with the Hubble horizon and Granda–Oliveros (GO) cutoffs. We have studied the behavior of a few quantities, such as dark energy density [Formula: see text], matter-energy density [Formula: see text], and skewness parameter [Formula: see text] and discuss their physical significances. In our THDE models, the EoS parameter explains the universe’s evolution based on the value of the non-extensive or Tsallis parameter [Formula: see text]. In addition, we develop the cosmographic parameters like, deceleration parameter [Formula: see text], jerk parameter [Formula: see text], lerk parameter [Formula: see text], snap parameter [Formula: see text] and maxout parameter [Formula: see text]. We have explored the [Formula: see text] plane and the stability analysis of the THDE model by a perturbation method. We have also constructed a correspondence between the THDE model with quintessence. Some physical and geometrical behaviors of the models are also discussed.

Thermodynamics of the Acceleration of the Universe in the κ(R, T) Gravity Model

In this article, we examined the behavior of dark energy (DE) and the cosmic acceleration in the framework of κ(R,T) gravity in the standard spherically symmetric coordinates (xi) = t,r,θ,ϕ, a spatially homogeneous and isotropic FLRW space–time. We discovered some remarkable cosmic characteristics in this investigation that are in line with both observations and the accepted ΛCDM model. We made two assumptions in order to determine a deterministic solution of the modified field equations (MFEs): (i) p=γρ, where γ(1≥γ≥0) is a constant, (ii) Λ = βH2, where β is an arbitrary constant. We solved the MFEs and obtained the expression for the Hubble parameter. The depicted model of κ(R,T) gravity was taken into consideration when discussing the behavior of the accelerating Universe. In κ(R,T) gravity, the statefinder analysis was utilized to distinguish our model from the ΛCDM model. The evolution of the cosmos was studied using an effective equation of state (EoS). We investigated the thermodynamic quantities and the generalized energy conditions in order to test the viability of our model. When dominant and weak energy conditions are satisfied, this validates the model; when the strong energy condition is not satisfied, this accelerates the expansion of the Universe.

Quintessence dark energy from strongly-coupled higgs mass gap: local and non-local higher-derivative non-perturbative scenarios

We entertain the possibility that dark energy arises from the Higgs field of quintessence type in the non-perturbative regimes. For this purpose we utilize a set of exact solutions of Higgs field theory recently devised, in terms of Jacobi elliptical function for a massless quartic scalar field, that satisfy a massive dispersion relation. In certain regions of the parameter space, determined by the quartic coupling value, we show that such solutions have the property to give the correct behavior for the equation of state of the dark energy depending on the initial theta value of periodicity of the Jacobi elliptical function solution. It is seen that on a time scale determined by the Hubble constant and the strength of the self-interaction of the scalar field, when conformal invariance is restored, the equation of state for the dark energy becomes manifest. Further we investigate scenarios within standard field theory framework and also extending to higher-derivative theories, namely infinite-derivative theory, motivated from p-adic string field theory, and Lee–Wick theories and in all cases, we find suitable choices of the parameter space leads to dark energy behavior of the Higgs field, which we compare.

Qualitative analysis for viscous cosmologies in a non linear regime of the Israel-Stewart formalism

We explore the dynamical properties of a cosmological model that includes viscous effects in the dark matter sector of the fluid equations in a flat Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetime. The bulk viscous effects are described by a non linear extension of the full Israel-Stewart model, which is a fluid causal scheme. We allow the interchange of energy in the dark sector and describe this by means of the interaction term, namely Q. We establish the dynamical system corresponding to Friedmann and fluid set of equations associated to the model and study the linear stability of its critical points. From the exploration of the dynamical system, we show the appearance of a critical point characterizing a de Sitter universe within the non interacting and interacting dark sector. We focus our study to analyse the stability of this fixed point in a large region of parameter space and derive linearized solutions around it. These approximate and analytical solutions are potentially able to describe the expansion of the universe since they are close to a de Sitter stationary solution. Within this regime with Q ≠ 0, we realize the existence of regions in the space of parameters where this critical point is stable and describes the behavior of dark energy as quintessence, cosmological constant and phantom like fluids. We perform a comparison between numerical and linearized solutions nearby the critical points within the full non linear regimes and also contrast them against ΛCDM model as a fiducial model. We find that the fully non linear regime is favored by observations and closer to the concordance model due to the non-zero value of the parameter j, which controls the non linear effects of bulk viscosity. In fact, at low redshift values, the expansion rate associated to the full non linear regime is practically indistinguishable from the ΛCDM model. The deceleration parameter obtained in this regime exhibits a transition from decelerated to accelerated cosmic expansion.

The phase-space view of non-local gravity cosmology

We consider non-local Integral Kernel Theories of Gravity in a homogeneous and isotropic universe background as a possible scenario to drive the cosmic history. In particular, we investigate the cosmological properties of a gravitational action containing the inverse d'Alembert operator of the Ricci scalar proposed to improve Einstein's gravity at both high and low-energy regimes. In particular, the dynamics of a physically motivated non-local exponential coupling is analyzed in detail by recasting the cosmological equations as an autonomous system of first-order differential equations with dimensionless variables. Consequently, we study the phase-space domain and its critical points, investigating their stability and main properties. In particular, saddle points and late-time cosmological attractors are discussed in terms of the free parameters of the model. Finally, we discuss the main physical consequences of our approach in view of dark energy behavior and the ΛCDM model.

Phantom model for Tsallis holographic dark energy

This paper considers Tsallis holographic dark energy in an FLRW universe that is flat, with the future event horizon serving as an IR cutoff. We examine the evolutionary behavior of parameters related to dark energy density and the equation of state for different values of Tsallis exponent [Formula: see text], and observe suitable behavior in the model. Here [Formula: see text] in lower redshift region corresponds to phantom behavior of Tsallis holographic dark energy. An effort is made to reconstruct the potential of the phantom for [Formula: see text] with lower redshift by examining the dynamics of the scalar field.

Quintessence model of Tsallis holographic dark energy

In order to apply entropy relations and holography to the entire universe, which is a gravitationally nonextensive framework, for consistency one should apply the standard definition for the universe horizon entropy, specifically Tsallis nonextensive entropy. The model of Tsallis holographic dark energy quantified by a new dimensionless parameter δ, which is a generalization of original holographic dark energy is an endeavour for testing the idea of dark energy inside the structure of holographic principle and entropy formalism. The Tsallis parameter δ decides the principle property of the Tsallis holographic dark energy. With the suitable choice of dimensionless parameter δ, this article attempts to analyse the behaviour of Tsallis holographic dark energy using the Tsallis entropy notion. The choice of δ<1 describes completely the quintessence behaviour of Tsallis holographic dark energy. The dynamics of the scalar field as well as potential of the quintessence is reconstructed for the choices of δ<1.

Reconsidering holographic dark energy in Brans\u2013Dicke theory

In this paper, we reconsider the concept of holographic dark energy in the framework of Brans–Dicke theory in the formalism of the flat Friedmann–Lemaitre–Robertson–Walker metric. Firstly, we demonstrate how the assumption phi propto a^n, where phi and a stand for the Brans–Dicke scalar field and scale factor, respectively, naturally leads to a constant deceleration parameter, irrespective of the energy content of the universe. Secondly, we consider interacting holographic dark energy with Hubble horizon as IR cut-off, and find the value of the Hubble parameter and corresponding value of the scale factor. Further, we find the value of the Brans–Dicke scalar field phi for the obtained value of the Hubble parameter and holographic dark energy. We obtain the corresponding value of the deceleration parameter and show that it can explain the phase transition of the universe. Moreover, statefinder diagnostics has been applied to compare the model with existing models. On the other hand, we consider the viscous behavior of holographic dark energy and show that the viscous holographic dark energy can play the role of interacting holographic dark energy as it is able to explain the phase transition of the universe. Further, we find the value of the Brans–Dicke scalar field phi for this viscous holographic dark energy. In this model also, we apply the statefinder diagnostic.