scholarly journals DENSITY PERTURBATIONS IN DECAYING HOLOGRAPHIC DARK ENERGY MODELS

2009 ◽  
Vol 24 (16) ◽  
pp. 1267-1275 ◽  
Author(s):  
KYOUNG YEE KIM ◽  
HYUNG WON LEE ◽  
YUN SOO MYUNG
Keyword(s):  
Dark Energy ◽  
Cold Dark Matter ◽  
Holographic Dark Energy ◽  
Accelerating Universe ◽  
Effective Equation ◽  
Small Perturbations ◽  
Energy Models ◽  
Negative Constant ◽  
Density Perturbations ◽  
Interacting Dark Energy Model

We study cosmological perturbations in the context of an interacting dark energy model, where the holographic dark energy with IR cutoff decays into the cold dark matter (CDM). For this purpose, we introduce three IR cutoffs of Hubble horizon, particle horizon, and future event horizon. Here we present small perturbations under the case that effective equation of state (EOS: ωeff) for the holographic energy density is determined to be the same negative constant as that for the CDM. Such new matter productions tend to dilute the density perturbations of CDM (matter contrast). For a decelerating universe of ωeff> -1/3, the matter contrast is growing as the universe evolves, while for an accelerating universe of ωeff< -1/3, the matter contrast is decaying, irrespective of the choice of IR cutoff. This shows clearly that the acceleration suppresses the growing of the density perturbations at the early universe.

scholarly journals Generalized entropies and corresponding holographic dark energy models

2020 ◽  
Vol 80 (8) ◽  
Author(s):  
H. Moradpour ◽  
A. H. Ziaie ◽  
M. Kord Zangeneh
Keyword(s):  
Black Holes ◽  
Dark Energy ◽  
Holographic Dark Energy ◽  
Apparent Horizon ◽  
Tsallis Entropy ◽  
Accelerating Universe ◽  
Frw Universe ◽  
Energy Models ◽  
Generalized Entropies ◽  
The Universe

Abstract Using Tsallis statistics and its relation with Boltzmann entropy, the Tsallis entropy content of black holes is achieved, a result in full agreement with a recent study (Mejrhit and Ennadifi in Phys Lett B 794:24, 2019). In addition, employing Kaniadakis statistics and its relation with that of Tsallis, the Kaniadakis entropy of black holes is obtained. The Sharma-Mittal and Rényi entropy contents of black holes are also addressed by employing their relations with Tsallis entropy. Thereinafter, relying on the holographic dark energy hypothesis and the obtained entropies, two new holographic dark energy models are introduced and their implications on the dynamics of a flat FRW universe are studied when there is also a pressureless fluid in background. In our setup, the apparent horizon is considered as the IR cutoff, and there is not any mutual interaction between the cosmic fluids. The results indicate that the obtained cosmological models have (i) notable powers to describe the cosmic evolution from the matter-dominated era to the current accelerating universe, and (ii) suitable predictions for the universe age.

scholarly journals Study of some cosmological parameters for interacting new holographic dark energy model in f(T) gravity

2016 ◽  
Vol 25 (01) ◽  
pp. 1650008
Author(s):  
Chayan Ranjit ◽  
Prabir Rudra
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cold Dark Matter ◽  
Holographic Dark Energy ◽  
Cosmological Parameters ◽  
Accelerating Universe ◽  
Friedmann Universe ◽  
Holographic Dark Energy Model ◽  
Eos Parameter ◽  
The Stability

The present work is based on the idea of an interacting framework of new holographic dark energy (HDE) with cold dark matter in the background of [Formula: see text] gravity. Here, we have considered the flat modified Friedmann universe for [Formula: see text] gravity which is filled with new HDE and dark matter. We have derived some cosmological parameters like deceleration parameter, equation of state (EoS) parameter, state-finder parameters, cosmographic parameters, Om parameter and graphically investigated the nature of these parameters for the above mentioned interacting scenario. The results are found to be consistent with the accelerating universe. Also, we have graphically investigated the trajectories in [Formula: see text] plane for different values of the interacting parameter and explored the freezing region and thawing region in [Formula: see text] plane. Finally, we have analyzed the stability of this model.

scholarly journals Tsallis, Rényi and Sharma-Mittal Holographic Dark Energy Models in Loop Quantum Cosmology

Symmetry ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 635 ◽  
Author(s):  
Abdul Jawad ◽  
Kazuharu Bamba ◽  
Muhammad Younas ◽  
Saba Qummer ◽  
Shamaila Rani
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Quantum Cosmology ◽  
Cold Dark Matter ◽  
Holographic Dark Energy ◽  
State Parameter ◽  
Loop Quantum Cosmology ◽  
Eos Parameter ◽  
Energy Models ◽  
The Universe

The cosmic expansion phenomenon is being studied through the interaction of newly proposed dark energy models (Tsallis, Rényi and Sharma-Mittal holographic dark energy (HDE) models) with cold dark matter in the framework of loop quantum cosmology. We investigate different cosmic implications such as equation of state parameter, squared sound speed and cosmological plane (ω d - ω d ′ , ω d and ω d ′ represent the equation of state (EoS) parameter and its evolution, respectively). It is found that EoS parameter exhibits quintom like behavior of the universe for all three models of HDE. The squared speed of sound represents the stable behavior of Rényi HDE and Sharma-Mittal HDE at the latter epoch while unstable behavior for Tsallis HDE. Moreover, ω d - ω d ′ plane lies in the thawing region for all three HDE models.

scholarly journals Taxonomy of Dark Energy Models

Universe ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 163
Author(s):  
Verónica Motta ◽  
Miguel A. García-Aspeitia ◽  
Alberto Hernández-Almada ◽  
Juan Magaña ◽  
Tomás Verdugo
Keyword(s):  
Dark Energy ◽  
Cold Dark Matter ◽  
Accelerated Expansion ◽  
Energy Component ◽  
The Past ◽  
Energy Models ◽  
The Status ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Unknown Component

The accelerated expansion of the Universe is one of the main discoveries of the past decades, indicating the presence of an unknown component: the dark energy. Evidence of its presence is being gathered by a succession of observational experiments with increasing precision in its measurements. However, the most accepted model for explaining the dynamic of our Universe, the so-called Lambda cold dark matter, faces several problems related to the nature of such energy component. This has led to a growing exploration of alternative models attempting to solve those drawbacks. In this review, we briefly summarize the characteristics of a (non-exhaustive) list of dark energy models as well as some of the most used cosmological samples. Next, we discuss how to constrain each model’s parameters using observational data. Finally, we summarize the status of dark energy modeling.

scholarly journals Physical Acceptability of the Renyi, Tsallis and Sharma-Mittal Holographic Dark Energy Models in the f(T,B) Gravity under Hubble’s Cutoff

Universe ◽  
2021 ◽  
Vol 7 (3) ◽  
pp. 67
Author(s):  
Salim Harun Shekh ◽  
Pedro H. R. S. Moraes ◽  
Pradyumn Kumar Sahoo
Keyword(s):  
Dark Energy ◽  
Holographic Dark Energy ◽  
Cosmological Parameters ◽  
Field Equations ◽  
Eos Parameter ◽  
Two Fluids ◽  
Gravitational Field Equations ◽  
Energy Models ◽  
Different Types ◽  
The Universe

In the present article, we investigate the physical acceptability of the spatially homogeneous and isotropic Friedmann–Lemâitre–Robertson–Walker line element filled with two fluids, with the first being pressureless matter and the second being different types of holographic dark energy. This geometric and material content is considered within the gravitational field equations of the f(T,B) (where T is the torsion scalar and the B is the boundary term) gravity in Hubble’s cut-off. The cosmological parameters, such as the Equation of State (EoS) parameter, during the cosmic evolution, are calculated. The models are stable throughout the universe expansion. The region in which the model is presented is dependent on the real parameter δ of holographic dark energies. For all δ≥4.5, the models vary from ΛCDM era to the quintessence era.

scholarly journals Holographic cosmology with two coupled fluids in the presence of viscosity

2021 ◽  
pp. 2150149
Author(s):  
I. Brevik ◽  
A. V. Timoshkin
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Holographic Dark Energy ◽  
Exponential Model ◽  
Point Of View ◽  
Accelerating Universe ◽  
Late Time ◽  
Conservation Of Energy ◽  
Analytical Expressions ◽  
Friedmann Robertson Walker

We explore the cosmological models of the late-time universe based on the holographic principle, taking into account the properties of the viscosity of the dark fluid. We use the mathematical formalism of generalized infrared cutoff holographic dark energy, as presented by Nojiri and Odintsov [Covariant generalized holographic dark energy and accelerating universe, Eur. Phys. J. C 77 (2017) 528]. We consider the Little Rip, the Pseudo Rip, and a bounce exponential model, with two interacting fluids, namely dark energy and dark matter in a spatially-flat Friedmann–Robertson–Walker universe. Within these models, analytical expressions are obtained for infrared cutoffs in terms of the particle horizons. The law of conservation of energy is presented, from a holographic point of view.

Cosmological implications of dark energy models in modified gravity

2018 ◽  
Vol 15 (03) ◽  
pp. 1850034 ◽  
Author(s):  
Nadeem Azhar ◽  
Abdul Jawad ◽  
Sarfraz Ahmad ◽  
Iftikhar Ahmed
Keyword(s):  
Dark Energy ◽  
Modified Gravity ◽  
Cold Dark Matter ◽  
Cosmological Parameters ◽  
Accelerated Expansion ◽  
Pilgrim Dark Energy ◽  
Energy Models ◽  
Expansion Of The Universe ◽  
Qcd Ghost Dark Energy ◽  
Chern Simons

We discuss the interacting modified QCD ghost dark energy and generalized ghost pilgrim dark energy with cold dark matter in the framework of dynamical Chern–Simons modified gravity. We investigate the cosmological parameters such as Hubble parameter, deceleration parameter and equation of state. We also discuss the physical significance of various cosmological planes like [Formula: see text] and statefinders. It is found that the results of cosmological parameters as well as planes explain the accelerated expansion of the Universe and are compatible with observational data.

scholarly journals UNIVERSE WITH HOLOGRAPHIC DARK ENERGY

MOMENTO ◽  
2020 ◽  
pp. 1-10
Author(s):  
Carlos Rodriguez-Benites ◽  
Mauricio Cataldo ◽  
Marcial Vásquez-Arteaga
Keyword(s):  
Dark Energy ◽  
Dark Energy Model ◽  
Cold Dark Matter ◽  
Holographic Dark Energy ◽  
Cosmological Parameters ◽  
Holographic Dark Energy Model ◽  
Dark Sector ◽  
Algebraic Expressions ◽  
Proposed Model ◽  
Λcdm Model

In this work we explore a Holographic Dark Energy Model in a flat Friedmann-LemaÎtre-Robertson-Walker Universe, which contains baryons, radiation, cold dark matter and dark energy within the framework of General Relativity. Furthermore, we consider three types of phenomenological interactions in the dark sector. With the proposed model we obtained the algebraic expressions for the cosmological parameters of our interest: the deceleration and coincidence parameters. Likewise, we graphically compare the proposed model with the ΛCDM model.

Sign in / Sign up

Export Citation Format

Share Document