Related papers: Testing the Cosmological Principle in the radio sk…
A new cosmological test is derived, based on the distribution of individual V/Vmax in a complete redshift-limited sample of distant objects. The fundamental assumption is that, in any bin of absolute luminosity, individual V/Vmax are…
We present the first study of the isotropy of the distribution of morphological types of galaxies in the Local Universe out to around 200 Mpc using more than 60,000 galaxies from the HyperLeda database. We divide the sky into two opposite…
There currently exist many observations which are not consistent with the cosmological principle. We review these observations with a particular emphasis on those relevant for Square Kilometre Array (SKA). In particular, several different…
Despite its fundamental importance in cosmology, there have been very few straight-forward tests of the cosmological principle. Such tests are especially timely because of the hemispherical asymmetry in the cosmic microwave background…
Modern cosmology rests on the working assumption that the Universe is isotropic and homogeneous at large scales. Here, we document a number of anomalous observations pointing to an anisotropic Universe in a direction consistent with the CMB…
We review the basic hypotheses which motivate the statistical framework used to analyze the cosmic microwave background, and how that framework can be enlarged as we relax those hypotheses. In particular, we try to separate as much as…
The cosmological principle assumes the isotropy of the Universe at large scales. It is a foundational assumption in the $\Lambda$CDM model, which is the current standard model of cosmology. Recent tensions give legitimacy to investigating…
Homogeneity is a crucial, but poorly tested, assumption in cosmology. We introduce a new approach which allows us to place limits on the presence of localized structures within essentially our entire observable volume, using cosmic…
We discuss inhomogeneous cosmological models which satisfy the Copernican principle. We construct some inhomogeneous cosmological models starting from the ansatz that the all the observers in the models view an isotropic cosmic microwave…
The Cosmological Principle states that the universe is statistically isotropic and homogeneous on large length scales, typically $\gtrsim 70$Mpc. A detection of significant deviation would help us falsify the simplest models of inflation.…
A combined sample of 79 high and low redshift supernovae Ia (SNe) is used to set constraints on the degree of anisotropy in the Universe out to $z\simeq1$. First we derive the global most probable values of matter density $\Omega_M $, the…
The standard model of cosmology is based on the hypothesis that the Universe is spatially homogeneous and isotropic. When interpreting most observations, this cosmological principle is applied stricto sensu: the light emitted by distant…
A nontrivial topology of the spatial section of the universe is an observable, which can be probed for all locally homogeneous and isotropic universes, without any assumption on the cosmological density parameters. We discuss how one can…
We test the tenet of statistical isotropy of the standard cosmological model via a homology analysis of the cosmic microwave background temperature maps. Examining small sectors of the normalized maps, we find that the results exhibit a…
The cosmic radio dipole is an anisotropy in the number counts of radio sources, analogous to the dipole seen in the cosmic microwave background (CMB). Measurements of source counts of large radio surveys have shown that though the radio…
The Cosmological Principle is a cornerstone of the standard model of cosmology and shapes how we view the Universe and our place within it. It is imperative, then, to devise multiple observational tests which can identify and quantify…
The Cosmological Principle is part of the foundation that underpins the standard model of the Universe. In the era of precision cosmology, when stress tests of the standard model are uncovering various tensions and possible anomalies, it is…
We study a uniform and isotropic cosmology with a decaying vacuum energy density, in the realm of a model with a time varying gravitational "constant". We show that, for late times, such a cosmology is in accordance with the observed values…
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…
The "cosmological principle" was set up early without realizing its implications for the horizon problem, and almost entirely without support from observational data. Consistent signals of anisotropy have been found in data on…