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Cosmography is a widely applied method to infer kinematics of the Universe at small cosmological scales while remaining agnostic about the theory of gravity at play. Usually cosmologists invoke the Friedmann-Lemaitre-Robertson-Walker (FLRW)…

Cosmology and Nongalactic Astrophysics · Physics 2025-11-25 Hayley J. Macpherson , Asta Heinesen

Most cosmological data analysis today relies on the Friedmann-Lemaitre-Robertson-Walker (FLRW) metric, providing the basis of the current standard cosmological model. Within this framework, interesting tensions between our increasingly…

Cosmology and Nongalactic Astrophysics · Physics 2021-12-01 Hayley J. Macpherson , Asta Heinesen

Anisotropies in the distance-redshift relation of cosmological sources are expected due to large-scale inhomogeneities in the local Universe. When the observed sources are tracing a large-scale matter flow in a general spacetime geometry,…

Cosmology and Nongalactic Astrophysics · Physics 2024-06-05 Julian Adamek , Chris Clarkson , Ruth Durrer , Asta Heinesen , Martin Kunz , Hayley J. Macpherson

The assumption of isotropy -- that the Universe looks the same in all directions on large scales -- is fundamental to the standard cosmological model. This model forms the building blocks of essentially all of our cosmological knowledge to…

Cosmology and Nongalactic Astrophysics · Physics 2022-12-29 Jessica A. Cowell , Suhail Dhawan , Hayley J. Macpherson

In this manuscript, we investigate the patterns satisfied by the cosmological anisotropy under the hypothesis of the observers being co-moving with a perfect fluid whose induced space sections are homogeneous with vanishing scalar…

General Relativity and Quantum Cosmology · Physics 2021-03-31 Leandro G. Gomes

The cosmological principle asserting the large-scale uniformity of the Universe is a testable assumption of the standard cosmological model. We explore the constraints on anisotropic expansion provided by measuring directional variation in…

Cosmology and Nongalactic Astrophysics · Physics 2025-04-07 Paula Boubel , Matthew Colless , Khaled Said , Lister Staveley-Smith

We calculate the off--center observational relations in a spherically symmetric dust universe that is inhomogeneous at small redshifts. In contrast to the usual model, in which the CMBR dipole is interpreted as a Doppler effect due to…

Astrophysics · Physics 2009-10-28 Neil Humphreys , Roy Maartens , David Matravers

Motivated by the back-reaction debate, and~some unexplained characteristics of the CMB, we investigate the possibility of some anisotropy in the universe observed around us. To this aim, we build up a novel prediction for the Hubble law for…

General Relativity and Quantum Cosmology · Physics 2024-10-10 Morgan Le Delliou , Maksym Deliyergiyev , Antonino Del Popolo

The redshift-distance modulus relation, the Hubble Diagram, derived from Cosmological General Relativity has been extended to arbitrarily large redshifts. Numerical methods were employed and a density function was found that results in a…

General Physics · Physics 2008-10-03 John G. Hartnett

We test claims of large-scale anisotropy in the local expansion rate using cluster scaling relations as distance indicators. Using a Bayesian forward model, we jointly fit the X-ray luminosity--temperature (LT) and thermal…

Cosmology and Nongalactic Astrophysics · Physics 2026-02-06 Tariq Yasin , Richard Stiskalek , Harry Desmond , Sebastian von Hausegger , Pedro G. Ferreira

We present a detailed analysis (including redshift tomography) of the cosmic dipoles in the Keck+VLT quasar absorber and in the Union2 SnIa samples. We show that the fine structure constant cosmic dipole obtained through the Keck+VLT quasar…

Cosmology and Nongalactic Astrophysics · Physics 2013-05-30 Antonio Mariano , Leandros Perivolaropoulos

Measurements of the cosmic redshift drift - the change in redshift of a source over time - will enable independent detection of cosmological expansion thanks to the immense precision soon reached by new facilities such as the Square…

Cosmology and Nongalactic Astrophysics · Physics 2025-10-16 Sofie Marie Koksbang , Asta Heinesen , Hayley J. Macpherson

We derive the prediction of the standard model of superluminal radio sources for the apparent transverse velocity of a radio source located at redshift z. The apparent velocity of the source is reduced by a factor of 1 + z compared to that…

Astrophysics · Physics 2009-11-10 Michal Chodorowski

In this paper we study an anisotropic model generated from a particular Bianchi type-III metric, which is a generalization of G\"odel's metric and an exact solution of Einstein's field equations. We analyse type Ia supernova data, namely…

Cosmology and Nongalactic Astrophysics · Physics 2013-04-02 R. S. Menezes , C. Pigozzo , S. Carneiro

The all-sky maps of the observed variation of the Hubble constant can be reproduced from a theoretical point of view by introducing an intergalactic plasma with a variable number density of electrons. The observed averaged value and…

Cosmology and Nongalactic Astrophysics · Physics 2014-09-30 L. Zaninetti

The gravitational coupling between large- and small-scale density perturbations leads to anisotropic distortions to the local small-scale matter fluctuations. Such local anisotropic distortions can be used to reconstruct the large-scale…

Cosmology and Nongalactic Astrophysics · Physics 2022-12-09 Shi-Hui Zang , Hong-Ming Zhu , Marcel Schmittfull , Ue-Li Pen

We investigate the distance-redshift relation in the simple void model. As discussed by Moffat and Tatarski, if the observer stays at the center of the void, the observed Hubble parameter is not so different from the background Hubble…

An expression for the average redshift drift in a statistically homogeneous and isotropic dust universe is given. The expression takes the same form as the expression for the redshift drift in FLRW models. It is used for a…

Cosmology and Nongalactic Astrophysics · Physics 2022-01-20 S. M. Koksbang , S. Hannestad

We consider the form of Hubble diagrams that would be constructed by observers in universes that are homogeneous but anisotropic, when averaged over suitably large length-scales. This is achieved by ray-tracing in different directions on…

General Relativity and Quantum Cosmology · Physics 2024-05-31 Theodore Anton , Timothy Clifton

The gravitational wave (GW) as a standard siren directly determines the luminosity distance from the gravitational waveform without reference to the specific cosmological model, of which the redshift can be obtained separately by means of…

Cosmology and Nongalactic Astrophysics · Physics 2018-05-09 Rong-Gen Cai , Tong-Bo Liu , Xue-Wen Liu , Shao-Jiang Wang , Tao Yang
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