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The prevailing cosmological model with the lambda-term, in which the space is flat, is studied (section 1). The corresponding age of the Universe (t0) is calculated (assuming a Hubble constant consistent with the measurements of the Hubble…

Astrophysics · Physics 2009-09-29 Evangelos Chaliasos

The Universe is neither homogeneous nor isotropic, but it is close enough that we can reasonably approximate it as such on suitably large scales. The inflationary-$\Lambda$-Cold Dark Matter ($\Lambda$CDM) concordance cosmology builds on…

Cosmology and Nongalactic Astrophysics · Physics 2023-03-08 Stefano Anselmi , Matthew F. Carney , John T. Giblin , Saurabh Kumar , James B. Mertens , Marcio ODwyer , Glenn D. Starkman , Chi Tian

Trace-free Einstein gravity, in the absence of matter fields and using the Friedmann-Robertson-Walker (FRW) metric, is solvable both classically and quantum mechanically. This is achieved by using the conformal time as the time variable and…

General Relativity and Quantum Cosmology · Physics 2025-06-06 Merced Montesinos , Abdel Pérez-Lorenzana , Jorge Meza , Diego Gonzalez

Over the last few years, low- and high-redshift observations set off a tension in the measurement of the present-day expansion rate, $H_0$. Adding to the riddle, observational data from the Planck mission point to a $3.4\sigma$ evidence for…

Cosmology and Nongalactic Astrophysics · Physics 2021-12-09 Ella Zuckerman , Luis A. Anchordoqui

The concordance of the $\Lambda$CDM cosmological model in light of current observations has been the subject of an intense debate in recent months. The 2018 Planck Cosmic Microwave Background (CMB) temperature anisotropy power spectrum…

Cosmology and Nongalactic Astrophysics · Physics 2021-07-02 Sunny Vagnozzi , Eleonora Di Valentino , Stefano Gariazzo , Alessandro Melchiorri , Olga Mena , Joseph Silk

Cosmography is an ideal tool to investigate the cosmic expansion history of the Universe in a model-independent way. The equations of motion in modified theories of gravity are usually very complicated; cosmography may select practical…

General Relativity and Quantum Cosmology · Physics 2021-01-04 Sanjay Mandal , Deng Wang , P. K. Sahoo

Current and upcoming surveys will measure the cosmological parameters with an extremely high accuracy. The primary goal of these observations is to eliminate some of the currently viable cosmological models created to explain the late time…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-20 Savvas Nesseris , Domenico Sapone

We revisit the observational constraints on spatial curvature following recent claims that the Planck data favour a closed Universe. We use a new and statistically powerful Planck likelihood to show that the Planck temperature and…

Cosmology and Nongalactic Astrophysics · Physics 2020-06-03 George Efstathiou , Steven Gratton

In [arXiv:2204.13980], we proposed and motivated a modification of the Einstein equation as a function of the topology of the Universe in the form of a bi-connection theory. The new equation features an additional "topological term" related…

General Relativity and Quantum Cosmology · Physics 2023-11-01 Quentin Vigneron , Vivian Poulin

We present a new cosmological test using the distribution of galaxies around cosmic voids without assuming a fiducial cosmology. The test is based on a physical model for the void-galaxy cross-correlation function projected along and…

Cosmology and Nongalactic Astrophysics · Physics 2019-04-10 Carlos M. Correa , Dante J. Paz , Nelson D. Padilla , Andrés N. Ruiz , Raúl E. Angulo , Ariel G. Sánchez

We investigate observational constraints on the running vacuum model (RVM) of $\Lambda=3\nu (H^{2}+K/a^2)+c_0$ in the spatially curved universe, where $\nu$ is the model parameter, $K$ corresponds to the spatial curvature constant, and…

Cosmology and Nongalactic Astrophysics · Physics 2020-09-29 Chao-Qiang Geng , Yan-Ting Hsu , Lu Yin , Kaituo Zhang

An intriguing discrepancy emerging in the concordance model of cosmology is the tension between the locally measured value of the Hubble rate, and the 'global' value inferred from the cosmic microwave background (CMB). This could be due to…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-18 Vinicius C. Busti , Chris Clarkson , Marina Seikel

Given observations of the standard candles and the cosmic chronometers, we apply Pad\'{e} parameterization to the comoving distance and the Hubble paramter to find how stringent the constraint is set to the curvature parameter by the data.…

Cosmology and Nongalactic Astrophysics · Physics 2020-01-08 Shi-Yu Li , Yun-Long Li , Tong-Jie Zhang , Tingting Zhang

Using comoving distance $d_c$ and angular diameter distance $d_A$, we recalculate parameters describing kinematical state of the universe, still combining the kinematical model of universe but not relying on dynamical equations for gravity.…

Cosmology and Nongalactic Astrophysics · Physics 2021-05-27 Hai Huang , Long Huang

In the realm of the $\omega$CDM cosmological model with quiescence or quintessence as the dark energy, characterized by $\omega>-1$, there exists a fixed value of $H(z)$ at $z=-1$, devoid of dependency on other cosmological parameters. To…

Cosmology and Nongalactic Astrophysics · Physics 2024-07-16 Cheqiu Lyu , Wei Hong , Tong-Jie Zhang

We present limits on the parameters of the o$\Lambda$CDM, $w_0$CDM, and $w_0 w_a$CDM models obtained from the joint analysis of the full-shape, baryon acoustic oscillations (BAO), big bang nucleosynthesis (BBN) and supernovae data. Our…

Cosmology and Nongalactic Astrophysics · Physics 2021-02-16 Anton Chudaykin , Konstantin Dolgikh , Mikhail M. Ivanov

Cosmological data have provided new constraints on the number of neutrino species and the neutrino mass. However these constraints depend on assumptions related to the underlying cosmology. Since a correlation is expected between the number…

Cosmology and Nongalactic Astrophysics · Physics 2013-05-30 Aaron Smith , Maria Archidiacono , Asantha Cooray , Francesco De Bernardis , Alessandro Melchiorri , Joseph Smidt

We apply Gaussian processes and Hubble function data in $f(T)$ cosmology, to reconstruct for the first time the $f(T)$ form in a model-independent way. In particular, using $H(z)$ datasets coming from cosmic chronometers as well as from the…

Cosmology and Nongalactic Astrophysics · Physics 2020-01-09 Yi-Fu Cai , Martiros Khurshudyan , Emmanuel N. Saridakis

A short inflationary phase may not erase all traces of the primordial universe. Associated observables include both spatial curvature and "anomalies" in the microwave background or large scale structure. The present curvature $\Omega_{K,0}$…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-25 Grigor Aslanyan , Richard Easther

The simplest cosmological model ($\Lambda$CDM) is well-known to suffer from the Hubble tension, namely an almost $5 \sigma$ discrepancy between the (model-based) early-time determination of the Hubble constant $H_0$ and its late-time (and…

Cosmology and Nongalactic Astrophysics · Physics 2023-10-06 Darshan Kumar , Debajyoti Choudhury , Debottam Nandi