scholarly journals SECOND-ORDER INVARIANTS AND HOLOGRAPHY

2012 ◽  
Vol 21 (12) ◽  
pp. 1250091 ◽  
Author(s):  
ORLANDO LUONGO ◽  
LUCA BONANNO ◽  
GERARDO IANNONE
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Holographic Dark Energy ◽  
Statistical Tests ◽  
A Priori ◽  
Second Order ◽  
Fine Tuning ◽  
Dark Energy Density ◽  
Event Horizons

Motivated by recent works on the role of the holographic principle in cosmology, we relate a class of second-order Ricci invariants to the IR cutoff characterizing the holographic dark energy density. The choice of second-order invariants provides an invariant way to account the problem of causality for the correct cosmological cutoff, since the presence of event horizons is not an a priori assumption. We find that these models work fairly well, by fitting the observational data, through a combined cosmological test with the use of SNeIa, BAO and CMB. This class of models is also able to overcome the fine-tuning and coincidence problems. Finally, to make a comparison with other recent models, we adopt the statistical tests AIC and BIC.

scholarly journals Cosmological Constant from the Entropy Balance Condition

2018 ◽  
Vol 2018 ◽  
pp. 1-5
Author(s):  
Merab Gogberashvili
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Apparent Horizon ◽  
Critical Density ◽  
Zero Energy ◽  
Dark Energy Density ◽  
Event Horizons ◽  
Balance Condition ◽  
Quantum Particles ◽  
Hubble Horizon

In the action formalism variations of metric tensors usually are limited by the Hubble horizon. On the contrary, variations of quantum fields should be extended up to the event horizon, which is the real boundary of the spacetime. As a result the entanglement energy of quantum particles across the apparent horizon is missed in the cosmological equations written for the Hubble volume. We identify this missing boundary term with the dark energy density and express it (using the zero energy assumption for the finite universe) as the critical density multiplied by the ratio of the Hubble and event horizons radii.

Holographic dark energy in a vector field cosmology

2015 ◽  
Vol 12 (10) ◽  
pp. 1550119 ◽  
Author(s):  
S. Davood Sadatian
Keyword(s):  
Dark Energy ◽  
Vector Field ◽  
Equation Of State ◽  
Energy Density ◽  
Holographic Dark Energy ◽  
Lorentz Invariance ◽  
Holographic Model ◽  
Dark Energy Density ◽  
Invariance Violation ◽  
Lorentz Invariance Violation

We obtain interacting holographic dark energy density in the framework of vector field cosmology (LIV). We consider possible modification of equation of state for the holographic energy density in lorentz invariance violation cosmology. In this case we select Jeans length as the IR cut-off in the holographic model. Then we consider the interaction between holographic energy densities ρΛ and ρm in this framework.

scholarly journals Some models of holographic dark energy on the Randall–Sundrum brane and observational data

2019 ◽  
Vol 29 (01) ◽  
pp. 1950176 ◽  
Author(s):  
A. V. Astashenok ◽  
A. S. Tepliakov
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Observational Data ◽  
Energy Analysis ◽  
Holographic Dark Energy ◽  
Brane Tension ◽  
Dark Energy Density ◽  
Energy Models ◽  
Current Energy ◽  
The Universe

Some models of holographic dark energy for Randall–Sundrum brane are considered. For the first class of dark energy models, we take energy density in the form [Formula: see text], where [Formula: see text] is size of event horizon in universe and [Formula: see text] is parameter (Tsallis holographic energy). Analysis of observational data allows to define upper limit on value of [Formula: see text] ([Formula: see text] is current energy density in the universe and [Formula: see text] is brane tension). Then we investigate models for which dark energy density has the form [Formula: see text] where [Formula: see text] is Hubble parameter.

Holographic Dark Energy Density and JBP Parametrization

2011 ◽  
Vol 50 (9) ◽  
pp. 2878-2883 ◽  
Author(s):  
Hassan Saadat ◽  
S. N. Mousavi ◽  
A. M. Saadat
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Holographic Dark Energy ◽  
Dark Energy Density

scholarly journals Cosmology in the mimetic higher-curvature $$f(R,R_{\mu \nu }R^{\mu \nu })$$ gravity

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Adam Z. Kaczmarek ◽  
Dominik Szczȩśniak
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Cosmological Model ◽  
Holographic Dark Energy ◽  
Scalar Potential ◽  
De Sitter ◽  
Field Equations ◽  
Dark Energy Density ◽  
Planck Data ◽  
Reconstruction Scheme

AbstractIn the framework of the mimetic approach, we study the $$f(R,R_{\mu \nu }R^{\mu \nu })$$ f ( R , R μ ν R μ ν ) gravity with the Lagrange multiplier constraint and the scalar potential. We introduce field equations for the discussed theory and overview their properties. By using the general reconstruction scheme we obtain the power law cosmology model for the $$f(R,R_{\mu \nu }R^{\mu \nu })=R+d(R_{\mu \nu }R^{\mu \nu })^p$$ f ( R , R μ ν R μ ν ) = R + d ( R μ ν R μ ν ) p case as well as the model that describes symmetric bounce. Moreover, we reconstruct model, unifying both matter dominated and accelerated phases, where ordinary matter is neglected. Using inverted reconstruction scheme we recover specific $$f(R,R_{\mu \nu }R^{\mu \nu })$$ f ( R , R μ ν R μ ν ) function which give rise to the de-Sitter evolution. Finally, by employing the perfect fluid approach, we demonstrate that this model can realize inflation consistent with the bounds coming from the BICEP2/Keck array and the Planck data. We also discuss the holographic dark energy density in terms of the presented $$f(R,R_{\mu \nu }R^{\mu \nu })$$ f ( R , R μ ν R μ ν ) theory. Thus, it is suggested that the introduced extension of the mimetic regime may describe any given cosmological model.

scholarly journals Role of generalized Ricci dark energy on a Chameleon field in the emergent universe

2011 ◽  
Vol 89 (9) ◽  
pp. 941-948 ◽  
Author(s):  
Surajit Chattopadhyay ◽  
Ujjal Debnath
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Energy Density ◽  
Holographic Dark Energy ◽  
Emergent Universe ◽  
Ricci Dark Energy ◽  
Associated Function

In this paper, we have considered the generalized Ricci dark energy (GRDE) and generalized holographic dark energy in the scenario of an emergent universe. Fractional energy density and deceleration parameters for GRDE were derived in an emergent universe scenario. Also, the role of GRDE on the chameleon field in the emergent universe scenario has been examined. Finally, the behaviours of the chameleon scalar field, [Formula: see text], corresponding potential, V, and associated function, f, were investigated in the presence of GRDE.

The role of anisotropy in holographic modified gravity

2014 ◽  
Vol 92 (5) ◽  
pp. 370-374
Author(s):  
V. Fayaz ◽  
H. Hossienkhani ◽  
M. Amirabadi ◽  
A. Aghamohammadi
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Energy Density ◽  
Modified Gravity ◽  
Holographic Dark Energy ◽  
Holographic Model ◽  
Holographic Dark Energy Model ◽  
Cosmological Implication ◽  
Reconstruction Scheme

In this paper, we study a cosmological implication of holographic dark energy in modified gravity. We employ the holographic model of dark energy to obtain the equation of state for the holographic energy density in a nonisotropic universe. The purpose of this work is to develop a reconstruction scheme for the modified gravity with f(R) action using the holographic energy density. Hence one can generate a phantom-like equation of state from a holographic dark energy model in a nonisotropic universe in the modified gravity cosmology framework.

scholarly journals HOLOGRAPHIC MODIFIED GRAVITY

2008 ◽  
Vol 17 (12) ◽  
pp. 2219-2228 ◽  
Author(s):  
M. R. SETARE
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Energy Density ◽  
Modified Gravity ◽  
Holographic Dark Energy ◽  
Holographic Dark Energy Model ◽  
Dark Energy Density ◽  
Reconstruction Scheme ◽  
Flat Universe ◽  
Cosmological Application

In this paper, we investigate cosmological application of holographic dark energy density in the modified gravity framework. We employ the holographic model of dark energy to obtain the equation of state for the holographic energy density in a spatially flat universe. Our calculation shows that, taking ΩΛ = 0.73 for the present time, it is possible to have wΛ crossing -1. This implies that one can generate a phantom-like equation of state from a holographic dark energy model in flat universe in the modified gravity cosmology framework. Also, we develop a reconstruction scheme for the modified gravity with f(R) action.

The scalar field models of Tsallis holographic dark energy with Granda-Oliveros cut-off in modified gravity

2021 ◽  
Author(s):  
Anirudh Pradhan ◽  
Gunjan Varshney ◽  
Umesh Kumar Sharma
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Holographic Dark Energy ◽  
Scalar Fields ◽  
Accelerated Expansion ◽  
Model Parameters ◽  
Frw Universe ◽  
Dark Energy Density ◽  
Eos Parameter ◽  
Expansion Of The Universe

This research explores the Tsallis holographic quintessence, k-essence, and tachyon model of dark energy in the modified f(R, T) gravity framework with Granda-Oliveros cutoff. We have analyzed the energy density through ρΛ = (αH<sup>2</sup> + βH)<sup>-δ+2</sup>. We study the correspondence between the quintessence, k-essence, and tachyon energy density with the Tsallis holographic dark energy density in a flat FRW Universe. The reconstruction is performed for the different values of Tsallis parameter δ in the region of ωΛ > -1 for the EoS parameter. This correspondence allows reconstructing the potentials and the dynamics for the scalar fields models, if we set some constraints for the model parameters, which describe the accelerated expansion of the Universe.

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