scholarly journals Simple-graduated dark energy and spatial curvature

2021 ◽  
Vol 104 (2) ◽  
Author(s):  
Giovanni Acquaviva ◽  
Özgür Akarsu ◽  
Nihan Katırcı ◽  
J. Alberto Vazquez
Keyword(s):  
Dark Energy ◽  
Spatial Curvature

scholarly journals Updated reduced CMB data and constraints on cosmological parameters

2015 ◽  
Vol 24 (10) ◽  
pp. 1550071 ◽  
Author(s):  
Rong-Gen Cai ◽  
Zong-Kuan Guo ◽  
Bo Tang
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Confidence Level ◽  
Cosmological Parameters ◽  
Hubble Constant ◽  
Spatial Curvature ◽  
Λcdm Model ◽  
The One

We obtain the reduced CMB data {lA, R, z∗} from WMAP9, WMAP9+BKP, Planck+WP and Planck+WP+BKP for the ΛCDM and wCDM models with or without spatial curvature. We then use these reduced CMB data in combination with low-redshift observations to put constraints on cosmological parameters. We find that including BKP results in a higher value of the Hubble constant especially when the equation of state (EOS) of dark energy and curvature are allowed to vary. For the ΛCDM model with curvature, the estimate of the Hubble constant with Planck+WP+Lensing is inconsistent with the one derived from Planck+WP+BKP at about 1.2σ confidence level (CL).

scholarly journals Flatness without CMB: The Entanglement of Spatial Curvature and Dark Energy Equation of State

2019 ◽  
Vol 877 (2) ◽  
pp. 107 ◽  
Author(s):  
Haoting Xu ◽  
Zhiqi Huang ◽  
Zhenjie Liu ◽  
Haitao Miao
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Energy Equation ◽  
Spatial Curvature

scholarly journals Tsallis holographic model of dark energy: Cosmic behavior, statefinder analysis and ωD–ωD′ pair in the nonflat universe

2019 ◽  
Vol 28 (15) ◽  
pp. 1950164 ◽  
Author(s):  
Vipin Chandra Dubey ◽  
Umesh Kumar Sharma ◽  
A. Beesham
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Deceleration Parameter ◽  
Holographic Dark Energy ◽  
Apparent Horizon ◽  
Density Parameter ◽  
Holographic Model ◽  
Spatial Curvature ◽  
Present Value ◽  
Evolutionary Trajectories

This paper investigates the Tsallis holographic dark energy (THDE) model in accordance with the apparent horizon as an infrared cut-off, in a non flat universe. The cosmological evolution of the deceleration parameter and equation of state of THDE model are calculated. The evolutionary trajectories are plotted for the THDE model for distinct values of the Tsallis parameter [Formula: see text] besides distinct spatial curvature contributions, in the statefinder [Formula: see text] parameter-pairs and [Formula: see text] plane, considering the present value of dark energy (DE) density parameter [Formula: see text], [Formula: see text], in the light of [Formula: see text] observational data. The statefinder and [Formula: see text] plane plots specify the feature of the THDE and demonstrate the separation between this framework and other models of DE.

scholarly journals A Thermodynamic Approach to Holographic Dark Energy

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Orlando Luongo
Keyword(s):  
Dark Energy ◽  
Holographic Dark Energy ◽  
Cosmological Models ◽  
Holographic Principle ◽  
Thermodynamic Approach ◽  
Free Term ◽  
Spatial Curvature ◽  
Massless Particles ◽  
Information Density ◽  
Minimal Information

We propose a method to relate the holographic minimal information density to de Broglie’s wavelength at a given universe temperature T. To figure this out, we assume that the thermal length of massive and massless constituents represents the cut-off scale of the holographic principle. To perform our analysis, we suppose two plausible universe volumes, that is, the adiabatic and the horizon volumes, that is, V∝a3 and V∝H-3, respectively, assuming zero spatial curvature. With these choices in mind, we evaluate the thermal lengths for massive and massless particles and we thus find two cosmological models associated with late and early cosmological epochs. We demonstrate that both models depend upon a free term β which enters the temperature parametrization in terms of the redshift z. For the two treatments, we show evolving dark energy terms which can be compared with the ωCDM quintessence paradigm when the barotropic factor takes the formal values ω0=-1/3(2+β) and ω0=-1/3(1+2β), respectively, for late and early eras. From our analyses, we nominate the two models as viable alternatives to dark energy determined from thermodynamics in the field of the holographic principle.

scholarly journals Astromechanics of Dual Universe: A New Possible Explanation for the Universe Unsolved Problems

2020 ◽  
Author(s):  
Mohammed B. Al-Fadhli
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Hubble Parameter ◽  
Polar Coordinates ◽  
Accelerated Expansion ◽  
Dark Side ◽  
Second Phase ◽  
Spatial Curvature ◽  
Evolution Of The Universe ◽  
The Universe

The necessity of the dark energy and dark matter in the present universe could be a consequence of the antimatter elimination assumption in the early universe. Current cosmological models that rely on the dark side have left many unsolved mysteries, remarkably: tension in Hubble parameter measurements, the accelerated expansion, the fast orbital speed of stars, the dark flow observations, cosmic horizon, space flatness, absent of the antimatter, etc. On the other hand, General Relativity (GR) has relied on the spacetime to demonstrate the movement of matter due to a local curvature caused by the presence of matter. Founded on this, I trace the evolution of the spacetime worldlines based on the evolution of the universe spatial scale factor and its evolution time in polar coordinates in order to construct a potential spatial curvature over the temporal dimension or a global spacetime curvature. The mathematical derivations of a positively curved universe governed by only gravity revealed two opposite solutions of the worldline evolution. This possibly implies that the matter and antimatter could be evolving in opposite directions as distinct sides of the universe. By implementing the derived model, we find a decelerated phase of spatial expansion during the first 10 Gyr, that is followed by a second phase of an accelerated expansion; potentially matching the tension in Hubble parameter measurements. In addition, the model predicts a final time-reversal phase of spatial contraction, due to rapid surge in density i.e. reversal entropy, leading to a Big Crunch of a cyclic universe. The predicted density is 1.14. Other predictions are (1) an evolvable curved spacetime at the decelerated phase that is transformed to flatness at the accelerated phase with internal voids which could continuously increase the matter and antimatter densities elsewhere in both sides. (2) the spatial curvature through time dimension along spacetime worldlines was found to increase galaxy orbital speed and (3) a calculable flow rate of the matter side towards the antimatter side at the accelerated phase; conceivably explaining the dark flow observation. These findings may indicate the existence of the antimatter as a distinct side, which influences the evolution of the universe instead of the dark energy or dark matter. These theoretical outcomes and predictions are promising, which can be verified, fine-tuned or disproved using astrometric data in future works.

Sign in / Sign up

Export Citation Format

Share Document