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We consider the influence of the perturbative bulk viscosity on the evolution of the Hubble parameter in the QCD era of the early Universe. For the geometry of the Universe we assume the homogeneous and isotropic…

General Relativity and Quantum Cosmology · Physics 2010-11-24 A. Tawfik , M. Wahba , H. Mansour , T. Harko

Recent research show that the cosmological components of the Universe should influence on the propagation of Gravitational Waves (GWs) and even it has been proposed a new way to measure the cosmological constant using Pulsar Timing Arrays…

Cosmology and Nongalactic Astrophysics · Physics 2020-12-08 Jorge Alfaro , Mauricio Gamonal

We use Hubble parameter versus redshift data from Stern, et al(2010) and Gazta\~{n}aga, et al (2009) to place constraints on model parameters of constant and time-evolving dark energy cosmological models. These constraints are consistent…

Cosmology and Nongalactic Astrophysics · Physics 2013-07-12 Yun Chen , Bharat Ratra

Using several cosmological observations, i.e. the cosmic microwave background anisotropies (WMAP), the weak gravitational lensing (CFHTLS), the measurements of baryon acoustic oscillations (SDSS+WiggleZ), the most recent observational…

Cosmology and Nongalactic Astrophysics · Physics 2012-12-07 Xin Wang , Xiao-Lei Meng , Tong-Jie Zhang , HuanYuan Shan , Yan Gong , Charling Tao , Xuelei Chen , Y. F. Huang

We investigate a four-parameter entropic dark energy model in a spatially curved FLRW universe, based on a generalized entropy-area relation at the apparent horizon. While the proposed entropy function captures a broad class of…

General Relativity and Quantum Cosmology · Physics 2025-11-21 Davood Momeni

We propose a model-independent way to determine the cosmic curvature using the Hubble parameter $H(z)$ measured with cosmic chronometers and the comoving distance $D(z)$ inferred from HII galaxies. We employ Gaussian processes to smooth the…

Cosmology and Nongalactic Astrophysics · Physics 2019-01-18 Jing Zheng , Fulvio Melia , Tong-Jie Zhang

We propose that whatever quantity controls the Heisenberg uncertainty relations (for a given complementary pair of observables) it should be identified with an effective Planck parameter. With this definition it is not difficult to find…

General Relativity and Quantum Cosmology · Physics 2021-03-17 John D. Barrow , Joao Magueijo

The cosmic spatial curvature parameter $\Omega_k$ is constrained, primarily by cosmic microwave background (CMB) data, to be very small. Observations of the cosmic distance ladder and the large scale structure can provide independent checks…

Cosmology and Nongalactic Astrophysics · Physics 2019-06-05 Haoting Xu , Zhiqi Huang , Zhenjie Liu , Haitao Miao

I discuss the Hubble parameter $H_0$, the age of the universe $t_0$, the density $\Omega_0$, and the cosmological constant $\Lambda$. To focus the discussion, I concentrate on the issue of the value of the density $\Omega_0$ in currently…

Astrophysics · Physics 2016-08-30 Joel R. Primack

In this paper, we go further and propose a cosmological model-independent approach to simultaneously determine the Hubble constant and cosmic curvature with strong lensing time-delay measurements, without any prior assumptions regarding the…

Cosmology and Nongalactic Astrophysics · Physics 2024-02-19 Tonghua Liu , Shuo Cao , Sixuan Zhang , Chenfa Zheng , Wuzheng Guo

The Hubble parameter H0 still not very well measured. Although the Hubble Key Project, Chandra and WMAP gave good estimates, the uncertainties remain quite large. In this brief report, we suggest an original and independent method to derive…

Astrophysics · Physics 2009-11-13 A. Barrau , A. Gorecki , J. Grain

We use the Risaliti & Lusso (2015) compilation of 808 X-ray and UV flux measurements of quasars (QSOs) in the redshift range $0.061 \leq z \leq 6.28$, alone and in conjuction with baryon acoustic oscillation (BAO) and Hubble parameter…

Cosmology and Nongalactic Astrophysics · Physics 2020-04-21 Narayan Khadka , Bharat Ratra

We investigate the constraint ability of the gravitational wave (GW) as the standard siren on the cosmological parameters by using the third-generation gravitational wave detector: the Einstein Telescope. We simulate the luminosity…

Cosmology and Nongalactic Astrophysics · Physics 2017-02-21 Rong-Gen Cai , Tao Yang

We revisit how super-Hubble cosmological fluctuations induce, at any time in the cosmic history, a non-vanishing spatial curvature of the local background metric. The random nature of these fluctuations promotes the curvature density…

Cosmology and Nongalactic Astrophysics · Physics 2023-12-06 Baptiste Blachier , Pierre Auclair , Christophe Ringeval , Vincent Vennin

We present cosmological parameter constraints on flat cosmologies dominated by dark energy using various cosmological data including the recent Archeops angular power spectrum measurements. A likelihood analysis of the existing Cosmic…

Astrophysics · Physics 2009-11-07 M. Douspis , A. Riazuelo , Y. Zolnierowski , A. Blanchard

In the standard Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmological model, the energy conditions provides model-independent bounds on the behavior of the distance modulus. However, this method can not provide us the detailed information…

Cosmology and Nongalactic Astrophysics · Physics 2021-01-20 Wen-Fei Liu , Jing Niu , Juan Li , Tong-Jie Zhang

This paper examines a cosmological model of scale-dependent gravity. The gravitational action is taken to be the Einstein-Hilbert term supplemented with a cosmological constant, where the couplings, $G_k$ and $\Lambda_k$, run with the…

General Relativity and Quantum Cosmology · Physics 2024-05-29 Pedro D. Alvarez , Benjamin Koch , Cristobal Laporte , Angel Rincon

In a pair of recent articles [PRL 105 (2010) 041302 - arXiv:1005.1132; JHEP 1103 (2011) 056 - arXiv:1012.2867] two of the current authors have developed an entropy bound for equilibrium uncollapsed matter using only classical general…

General Relativity and Quantum Cosmology · Physics 2017-11-29 Gabriel Abreu , Carlos Barcelo , Matt Visser

We study the performance of the latest $H(z)$ data in constraining the cosmological parameters of different cosmological models, including that of Chevalier-Polarski-Linder $w_{0}w_{1}$ parametrization. First, we introduce a statistical…

Cosmology and Nongalactic Astrophysics · Physics 2018-03-07 Fotios Anagnostopoulos , Spyros Basilakos

Using the relation between distance modulus $(m - M)$ and redshift $z$, deduced from Friedman- Robertson-Walker (FRW) metric and assuming different values of deceleration parameter $q_0$. We constrained the Hubble parameter $h$. The…

General Physics · Physics 2016-06-03 C. C. Onuchukwu , A. C. Ezeribe