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

2021 ◽  
pp. 2150154
Author(s):  
Roman Neomenko
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Coupling Parameter ◽  
Gravitational Interaction ◽  
State Parameter ◽  
Model Parameters ◽  
Cosmological Perturbations ◽  
Energy Models ◽  
The Impact ◽  
Dynamical Dark Energy

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.

scholarly journals FORMATION OF DARK MATTER HALOES IN A HOMOGENEOUS DARK ENERGY UNIVERSE

2010 ◽  
Vol 19 (08n10) ◽  
pp. 1397-1403
Author(s):  
L. MARASSI
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Large Scale ◽  
State Parameter ◽  
Mass Function ◽  
Accelerated Expansion ◽  
X Ray ◽  
Energy Models ◽  
Dark Energy Component ◽  
Standard Press

Several independent cosmological tests have shown evidences that the energy density of the universe is dominated by a dark energy component, which causes the present accelerated expansion. The large scale structure formation can be used to probe dark energy models, and the mass function of dark matter haloes is one of the best statistical tools to perform this study. We present here a statistical analysis of mass functions of galaxies under a homogeneous dark energy model, proposed in the work of Percival (2005), using an observational flux-limited X-ray cluster survey, and CMB data from WMAP. We compare, in our analysis, the standard Press–Schechter (PS) approach (where a Gaussian distribution is used to describe the primordial density fluctuation field of the mass function), and the PL (power–law) mass function (where we apply a non-extensive q-statistical distribution to the primordial density field). We conclude that the PS mass function cannot explain at the same time the X-ray and the CMB data (even at 99% confidence level), and the PS best fit dark energy equation of state parameter is ω = -0.58, which is distant from the cosmological constant case. The PL mass function provides better fits to the HIFLUGCS X-ray galaxy data and the CMB data; we also note that the ω parameter is very sensible to modifications in the PL free parameter, q, suggesting that the PL mass function could be a powerful tool to constrain dark energy models.

scholarly journals Barotropic fluid compatible parametrizations of dark energy

2020 ◽  
Vol 80 (7) ◽  
Author(s):  
Dalibor Perković ◽  
Hrvoje Štefančić
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Speed Of Sound ◽  
Functional Form ◽  
State Parameter ◽  
Model Parameters ◽  
Barotropic Fluid ◽  
Energy Models ◽  
Equation Of State Parameter ◽  
Fundamental Requirement

Abstract Parametrizations of equation of state parameter as a function of the scale factor or redshift are frequently used in dark energy modeling. The question investigated in this paper is if parametrizations proposed in the literature are compatible with the dark energy being a barotropic fluid. The test of this compatibility is based on the functional form of the speed of sound squared, which for barotropic fluid dark energy follows directly from the function for the Equation of state parameter. The requirement that the speed of sound squared should be between 0 and speed of light squared provides constraints on model parameters using analytical and numerical methods. It is found that this fundamental requirement eliminates a large number of parametrizations as barotropic fluid dark energy models and puts strong constraints on parameters of other dark energy parametrizations.

scholarly journals Interacting dark side of universe through generalized uncertainty principle

2019 ◽  
Vol 28 (06) ◽  
pp. 1950081
Author(s):  
M. Rashki ◽  
M. Fathi ◽  
B. Mostaghel ◽  
S. Jalalzadeh
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Uncertainty Principle ◽  
Generalized Uncertainty Principle ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Dark Side ◽  
Late Time ◽  
Doubly Special Relativity ◽  
The Impact

We investigate the impact of the generalized uncertainty principle proposed by some approaches to quantum gravity such as string theory and doubly special relativity on the cosmology. Using generalized Poisson brackets, we obtain the modified Friedmann and Raychaudhuri equations and suggest a dynamical dark energy to explain the late-time acceleration of the universe. After considering the interaction between dark matter and dark energy, originated from the minimal length, we obtain the effective cosmological parameters and equation of state parameter for dark matter and dark energy. Finally, we show that the resulting model is equivalent to the Phantom and Tachyon fields.

A VARIABLE MODIFIED CHAPLYGIN GAS MODEL WITH INTERACTION

2009 ◽  
Vol 18 (12) ◽  
pp. 1851-1862 ◽  
Author(s):  
LILI XING ◽  
YUANXING GUI ◽  
CHUNYAN WANG
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
State Parameter ◽  
Chaplygin Gas ◽  
Modified Chaplygin Gas ◽  
Phantom Divide ◽  
Energy Models ◽  
Big Rip ◽  
Variable Modified Chaplygin Gas ◽  
The Future

We consider in this paper a variable modified Chaplygin gas (VMCG) model for describing the unification of dark energy and dark matter, in which dark energy interacts with dark matter. Concretely, the evolution of the VMCG model with interaction is discussed and the statefinder diagnostic for the model is performed. By analysis, we find that the effective state parameter of dark energy can cross the phantom divide wΛ= -1 and our universe will not end up with a Big Rip in the future. Furthermore, we perform a statefinder analysis on this scenario and show the discrimination between this scenario and other dark energy models.

scholarly journals Study of thermal stability for different dark energy models

2019 ◽  
Vol 16 (11) ◽  
pp. 1950171
Author(s):  
Abdulla Al Mamon ◽  
Pritikana Bhandari ◽  
Subenoy Chakraborty
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cold Dark Matter ◽  
State Parameter ◽  
Chaplygin Gas ◽  
Point Of View ◽  
Frw Universe ◽  
Generalized Chaplygin Gas ◽  
Dark Fluid ◽  
Energy Models

In this work, we have made an attempt to investigate the dark energy possibility from the thermodynamical point of view. For this purpose, we have studied thermodynamic stability of three popular dark energy models in the framework of an expanding, homogeneous, isotropic and spatially flat FRW Universe filled with dark energy and cold dark matter. The models considered in this work are Chevallier–Polarski–Linder (CPL) model, Generalized Chaplygin Gas (GCG) model and Modified Chaplygin Gas (MCG) model. By considering the cosmic components (dark energy and cold dark matter) as perfect fluid, we have examined the constraints imposed on the total equation of state parameter ([Formula: see text]) of the dark fluid by thermodynamics and found that the phantom nature ([Formula: see text]) is not thermodynamically stable. Our investigation indicates that the dark fluid models (CPL, GCG and MCG) are thermodynamically stable under some restrictions of the parameters of each model.

scholarly journals Model Independent Diagnostics in Interacting Dark Energy Models

Universe ◽  
2020 ◽  
Vol 6 (4) ◽  
pp. 49
Author(s):  
Ying Jiang ◽  
Zhongxu Han ◽  
Qian Zhang ◽  
Weiqiang Yang ◽  
Yabo Wu ◽  
...  
Keyword(s):  
Dark Energy ◽  
Dark Energy Model ◽  
Cold Dark Matter ◽  
Coupling Parameter ◽  
Gravitational Interaction ◽  
Coupled Model ◽  
State Parameter ◽  
Energy Model ◽  
The State ◽  
Eos Parameter

In this paper, we have explored non-gravitational interaction dark energy model between dark energy and cold dark matter (CDM). The main purpose of this work is to explore the deviations from Λ C D M and to distinguish the evolution trajectory of the interaction dark energy model with different parameters. Six forms of interaction were focused on. We have analyzed the deceleration parameters of the coupled model and explored the theoretical models through s t a t e f i n d e r h i e r a r c h y and the O m diagnostic. We have considered that the Equation of State (EoS) parameter w and parameter ξ take different values on the interaction dark energy model respectively and keep another parameter unchanged. It was found that q ( z ) is the worst of the four diagnoses. O m , S 3 ( 1 ) and S 4 ( 1 ) are good tools to distinguish the interaction dark energy model from Λ C D M . S 3 ( 1 ) is a better diagnostic tool when the state parameter w changes and the coupling parameter ξ is fixed, while S 4 ( 1 ) works better when the coupling parameter ξ changes and the state parameter w is fixed.

scholarly journals Quintessence and Holographic Dark Energy infTGravity

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
M. Zubair
Keyword(s):  
Dark Energy ◽  
Dark Energy Model ◽  
Holographic Dark Energy ◽  
State Parameter ◽  
Energy Model ◽  
Cosmic Acceleration ◽  
Model Parameters ◽  
Efficient Tool ◽  
Future Evolution ◽  
Energy Models

We regardfTtheory as an efficient tool to explain the current cosmic acceleration and associate its evolution with the known dark energy models. The numerical scheme is applied to reconstructfTtheory from dark energy model with constant equation of state parameter and holographic dark energy model. We set the model parametersωϑandcas describing the different evolution eras and show the distinctive behavior of each case realized infTtheory. We also present the future evolution of reconstructedfTand find that it is consistent with the recent observations.

scholarly journals Cosmological Consequences of New Dark Energy Models in Einstein-Aether Gravity

Symmetry ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 509 ◽  
Author(s):  
Shamaila Rani ◽  
Abdul Jawad ◽  
Kazuharu Bamba ◽  
Irfan Malik
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Graphical Representation ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Effective Density ◽  
Evolutionary Equation ◽  
Model Parameters ◽  
Energy Models ◽  
Equation Of State Parameter

In this paper, we reconstruct various solutions for the accelerated universe in the Einstein-Aether theory of gravity. For this purpose, we obtain the effective density and pressure for Einstein-Aether theory. We reconstruct the Einstein-Aether models by comparing its energy density with various newly proposed holographic dark energy models such as Tsallis, Rényi and Sharma-Mittal. For this reconstruction, we use two forms of the scale factor, power-law and exponential forms. The cosmological analysis of the underlying scenario has been done by exploring different cosmological parameters. This includes equation of state parameter, squared speed of sound and evolutionary equation of state parameter via graphical representation. We obtain some favorable results for some values of model parameters

Anisotropic behavior of dark energy models in fractal cosmology

2018 ◽  
Vol 15 (12) ◽  
pp. 1850200 ◽  
Author(s):  
H. Hossienkhani ◽  
H. Yousefi ◽  
N. Azimi
Keyword(s):  
Dark Energy ◽  
State Parameter ◽  
Acoustic Oscillation ◽  
Linear Perturbation ◽  
Model Parameters ◽  
De Sitter ◽  
Ghost Dark Energy ◽  
Energy Models ◽  
The Universe ◽  
Generalized Ghost Dark Energy

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

scholarly journals Constraints on dark matter-photon coupling in the presence of time-varying dark energy

2019 ◽  
Vol 35 (04) ◽  
pp. 1950358
Author(s):  
Santosh Kumar Yadav
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Large Scale ◽  
Coupling Parameter ◽  
Coupling Model ◽  
Model Parameters ◽  
Time Varying ◽  
Acoustic Oscillations ◽  
Eos Parameter ◽  
Photon Coupling

In a recent work [S. Kumar, R. C. Nunes and S. K. Yadav, Phys. Rev. D 98, 043521 (2018)], we have investigated a dark matter (DM)-photon coupling model in which the DM decays into photons in the presence of dark energy (DE) with constant equation of state (EoS) parameter. Here, we study an extension of the DM-photon coupling model by considering a time-varying EoS of DE via Chevalier–Polarski–Linder (CPL) parametrization. We derive observational constraints on the model parameters by using the data from cosmic microwave background (CMB), baryonic acoustic oscillations (BAO), the local value of Hubble constant from Hubble Space Telescope (HST), and large-scale structure (LSS) information from the abundance of galaxy clusters, in four different combinations. We find that in this DM-photon coupling scenario the mean values of [Formula: see text] are in quintessence region [Formula: see text] whereas they were in the phantom region [Formula: see text] in our previous study with all data combinations. The constraints on the DM-photon coupling parameter do not reflect any significant deviation from the previous results. Due to the decay of DM into photons, we obtain higher values of [Formula: see text], consistent with the local measurements, similar to our previous study. But, the time-varying DE leads to lower values of [Formula: see text] in the DM-photon coupling model with all data combinations, in comparison to the results in our previous study. Thus, allowing time-varying DE in the DM-photon coupling scenario is useful to alleviate the [Formula: see text] and [Formula: see text] tensions.

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