scholarly journals Holographic dark energy in Rastall theory

2020 ◽  
Vol 35 (33) ◽  
pp. 2050276
Author(s):  
S. Ghaffari ◽  
A. A. Mamon ◽  
H. Moradpour ◽  
A. H. Ziaie
Keyword(s):  
Dark Energy ◽  
Hubble Parameter ◽  
Vacuum Energy ◽  
Holographic Dark Energy ◽  
Tsallis Entropy ◽  
Text Data ◽  
New Approach ◽  
Redshift Range ◽  
Data Points

Bearing holographic dark energy hypothesis in mind, the ability of vacuum energy in describing the current accelerated universe is studied in the framework of Rastall theory. Here, in addition to the ordinary approach in which it is expected that this energy plays the role of dark energy, we also address a new approach where the sum of this energy and Rastall term is responsible for the current accelerated universe. We also investigate the cosmological outcomes of using Tsallis entropy in quantifying the energy of fields in vacuum for both mentioned approaches. The implications of considering an interaction between the various segments of cosmic fluid have been addressed in each studied cases. The normalized Hubble parameter for the models have also been plotted and compared that with the [Formula: see text] data consisting of 41 data points in the redshift range of [Formula: see text].

scholarly journals Hubble Parameter Measurement Constraints on Holographic Dark Energy

2019 ◽  
Vol 206 ◽  
pp. 09013
Author(s):  
Plato Lum You Sheng ◽  
Cindy Ng Shao Chin
Keyword(s):  
Dark Energy ◽  
Hubble Parameter ◽  
Dark Energy Model ◽  
Holographic Dark Energy ◽  
Energy Model ◽  
Parameter Measurement ◽  
Apparent Magnitude ◽  
Holographic Dark Energy Model ◽  
Data Points

We review and attempt to constrain the ΛCDM and XCDM models using 26 Hubble parameter against redshift data points from [1], [2], [3], [4] and [5]. Also known as the cosmic chronometers approach, these constraints are now almost as restrictive as or less than those from Type 1a Supernova (SN1a) apparent magnitude versus redshift data [6]. Then, we attempt to constrain the Holographic Dark Energy model [7] using the aforementioned 26 H(z) measurement. Although interesting, errors for the H(z) could be less well estimated as it is a relatively new measure relative to SN1a data, which has been studied for a much longer time.

scholarly journals Do we come from a quantum anomaly?

2019 ◽  
Vol 28 (14) ◽  
pp. 1944002 ◽  
Author(s):  
Spyros Basilakos ◽  
Nick E. Mavromatos ◽  
Joan Solà Peracaula
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Energy Density ◽  
Hubble Parameter ◽  
Vacuum Energy ◽  
Vacuum Energy Density ◽  
Quantum Anomaly ◽  
Inflationary Phase ◽  
Axion Field ◽  
The Universe

We present a string-based picture of the cosmological evolution in which (CP-violating) gravitational anomalies acting during the inflationary phase of the universe cause the vacuum energy density to “run” with the effective Hubble parameter squared, [Formula: see text], thanks to the axion field of the bosonic string multiplet. This leads to baryogenesis through leptogenesis with massive right-handed neutrinos. The generation of chiral matter after inflation helps in cancelling the anomalies in the observable radiation- and matter-dominated eras. The present era inherits the same “running vacuum” structure triggered during the inflationary time by the axion field. The current dark energy is thus predicted to be mildly dynamical, and dark matter should be made of axions. Paraphrasing Carl Sagan [ https://www.goodreads.com/author/quotes/10538.Carl_Sagan .]: we are all anomalously made from starstuff.

scholarly journals Holographic dark energy model in unimodular f(T) gravity

2019 ◽  
Vol 16 (01) ◽  
pp. 1950003
Author(s):  
A. E. Godonou ◽  
M. J. S. Houndjo ◽  
J. Tossa
Keyword(s):  
Dark Energy ◽  
Holographic Dark Energy ◽  
Teleparallel Gravity ◽  
De Sitter ◽  
Holographic Dark Energy Model ◽  
Reconstruction Procedure ◽  
Perfect Agreement ◽  
Text Data ◽  
Viable Model ◽  
Reconstructed Model

This work deals with holographic dark energy in the context of unimodular [Formula: see text] gravity, which is a modification of teleparallel gravity. We develop the general reconstruction procedure of the [Formula: see text] form that can yield the holographic feature of the dark energy. We fit the reconstructed model with the [Formula: see text] data and our results show a perfect agreement with the WMAP9 cosmological observational data, at least for the range [Formula: see text]. We investigate the consistency of the reconstructed model by studying its stability against linear gravitational and matter perturbations, fixing [Formula: see text] to [Formula: see text]. The model presents stability for both de Sitter and power-law solutions and we conclude that it is a good candidate as alternative viable model for characterizing holographic dark energy.

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 DARK ENERGY: A UNIFYING VIEW

2008 ◽  
Vol 17 (03n04) ◽  
pp. 651-658 ◽  
Author(s):  
WINFRIED ZIMDAHL
Keyword(s):  
Dark Energy ◽  
Holographic Dark Energy ◽  
Interaction Strength ◽  
Chaplygin Gas ◽  
Accelerated Expansion ◽  
Strength Parameter ◽  
Expansion Of The Universe ◽  
Pressure Perturbations ◽  
The Universe

Different models of the cosmic substratum which pretend to describe the present stage of accelerated expansion of the Universe, like the ΛCDM model or the Chaplygin gas, can be seen as special realizations of a holographic dark energy cosmology if the option of an interaction between pressureless dark matter and dark energy is taken seriously. The corresponding interaction strength parameter plays the role of a cosmological constant. Differences occur at the perturbative level. In particular, the pressure perturbations are intrinsically nonadiabatic.

Diagnosing Tsallis holographic dark energy models with statefinder and ω − ω′ pair

2019 ◽  
Vol 34 (13) ◽  
pp. 1950101 ◽  
Author(s):  
Umesh Kumar Sharma ◽  
Anirudh Pradhan
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Holographic Dark Energy ◽  
Tsallis Entropy ◽  
Observation Data ◽  
Energy Models ◽  
Evolutionary Trajectories

A useful method, known as statefinder diagnostic, which may differentiate one dark energy (DE) model from others is applied in this work to a holographic dark energy (HDE) model from Tsallis entropy, called the Tsallis holographic dark energy (THDE) model. The evolutionary trajectories of this model are plotted in the statefinder parameter — planes and [Formula: see text] plane, and it is observed that the parameter [Formula: see text] of this model plays a magnificent role from the statefinder and [Formula: see text] plane viewpoints. Eventually, the evolutionary trajectories are plotted considering two different values of THDE energy density ([Formula: see text]), [Formula: see text], in the light of Planck 2018 results VI base-LCDM cosmology and [Formula: see text], in the light of SNe + BAO + OHD + CMB observation data.

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.

ANISOTROPIC UNIVERSE WITH HESSENCE DARK ENERGY

2010 ◽  
Vol 19 (13) ◽  
pp. 2071-2078 ◽  
Author(s):  
SHUVENDU CHAKRABORTY ◽  
UJJAL DEBNATH
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Anisotropic Universe ◽  
Field Equations ◽  
Complex Scalar ◽  
New Approach ◽  
Bianchi I ◽  
Scale Factors ◽  
Complex Scalar Field

In this work, we have considered a noncanonical complex scalar field named hessence to play the role of quintom in anisotropic universe (particularly in the Bianchi I model) as a new approach to look into the unknown mysterious world of dark energy. We have solved the field equations by considering the power-law form of scale factors and found the potential function in terms of ϕ with some restrictions. We also show here that hessence can avoid the Q-ball formation in anisotropic universe.

scholarly journals DARK ENERGY AND QCD GHOST

2012 ◽  
Vol 07 ◽  
pp. 194-201
Author(s):  
NOBUYOSHI OHTA
Keyword(s):  
Dark Energy ◽  
Hubble Parameter ◽  
Vacuum Energy ◽  
Mass Scale ◽  
Time Dependent ◽  
Accelerating Expansion ◽  
Expansion Of The Universe ◽  
The Right ◽  
The Universe

We argue that the dark energy that explains the observed accelerating expansion of the universe may arise due to the contribution to the vacuum energy of the QCD ghost in a time-dependent background. We show that the QCD ghost produces dark energy proportional to the Hubble parameter [Formula: see text] (ΛQCD is the QCD mass scale) which has the right magnitude ~ (3 × 10-3 eV)4.

scholarly journals Statefinder and Om Diagnostics for New Generalized Chaplygin Gas Model

Universe ◽  
2021 ◽  
Vol 7 (10) ◽  
pp. 362
Author(s):  
Abdulla Al Mamon ◽  
Vipin Chandra Dubey ◽  
Kazuharu Bamba
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Observational Data ◽  
Hubble Parameter ◽  
Chaplygin Gas ◽  
Distance Modulus ◽  
Generalized Chaplygin Gas ◽  
New Model ◽  
Λcdm Model ◽  
Data Points

We explore a unified model of dark matter and dark energy. This new model is a generalization of the generalized Chaplygin gas model and is known as a new generalized Chaplygin gas (NGCG) model. We study the evolutions of the Hubble parameter and the distance modulus for the model under consideration and the standard ΛCDM model and compare that with the observational datasets. Furthermore, we demonstrate two geometric diagnostics analyses including the statefinder (r,s) and Om(z) to the discriminant NGCG model from the standard ΛCDM model. The trajectories of evolution for (r,s) and Om(z) diagnostic planes are shown to understand the geometrical behavior of the NGCG model by using different observational data points.

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