Is the observable Universe consistent with the cosmological principle?

Abstract

The Cosmological Principle (CP) -- the notion that the Universe is spatially isotropic and homogeneous on large scales -- underlies a century of progress in cosmology. It is conventionally formulated through the Friedmann-Lema\^{\i}tre-Robertson-Walker (FLRW) cosmologies as the spacetime metric, and culminates in the successful and highly predictive $\Lambda$-Cold-Dark-Matter ($\Lambda$CDM) model. Yet, tensions have emerged within the $\Lambda$CDM model, most notably a statistically significant discrepancy in the value of the Hubble constant, $H_0$. Since the notion of cosmic expansion determined by a single parameter is intimately tied to the CP, implications of the $H_0$ tension may extend beyond $\Lambda$CDM to the CP itself. This review surveys current observational hints for deviations from the expectations of the CP, highlighting synergies and disagreements that warrant further study. Setting aside the debate about individual large structures, potential deviations from the CP include variations of cosmological parameters on the sky, discrepancies in the cosmic dipoles, and mysterious alignments in quasar polarizations and galaxy spins. While it is possible that a host of observational systematics are impacting results, it is equally plausible that precision cosmology may have outgrown the FLRW paradigm, an extremely pragmatic but non-fundamental symmetry assumption.

Reanalysis of the spin direction distribution of Galaxy Zoo SDSS spiral galaxies

“…The data and code are available publicly to allow replication of the results. The possible scientific implications and the agreement of the observation with several other recent studies that make use of other probes (Aluri et al, 2022;Luongo et al, 2022;Dainotti et al, 2022;Yeung and Chu, 2022;Hou et al, 2022;Philcox, 2022) are discussed in Section 5. Data for the experiments performed in this paper is made publicly available to allow reproduction of the results and further related experiments.…”

“…If these observations reflect the real large-scale structure of the Universe, they shift from the Cosmological Principle and the standard cosmological models (Aluri et al, 2022), and can be related to several alternative theories. These include ellipsodial Universe (Campanelli et al, 2006(Campanelli et al, , 2011Gruppuso, 2007;Cea, 2014), rotating Universe (Gödel, 1949;Ozsváth and Schücking, 1962;Ozsvath and Schücking, 2001;Sivaram and Arun, 2012;Chechin, 2016;Seshavatharam and Lakshminarayana, 2020a;Campanelli, 2021), or black hole cosmology (Pathria, 1972;Easson and Brandenberger, 2001;Seshavatharam and Lakshminarayana, 2014;Pop lawski, 2010;Tatum et al, 2018;Christillin, 2014;Seshavatharam and Lakshminarayana, 2020b;Chakrabarty et al, 2020).…”

“…While the assumption that the Universe is isotropic is part of the Cosmological Principle, several different probes have shown non-random distribution at cosmological scales (Aluri et al, 2022). These probes include the CMB radiation (Eriksen et al, 2004;Cline et al, 2003;Gordon and Hu, 2004;Campanelli et al, 2007;Copi et al, 2010;Zhe et al, 2015;Ashtekar et al, 2021;Yeung and Chu, 2022;Greco et al, 2022), as well as other probes such as LX-T scaling (Migkas et al, 2020), cosmic rays (Aab et al, 2017), short gamma ray bursts (Mészáros, 2019), Ia supernova (Javanmardi et al, 2015;Lin et al, 2016), dark energy (Adhav et al, 2011;Adhav, 2011;Perivolaropoulos, 2014;Colin et al, 2019), quasars (Secrest et al, 2021a;Zhao and Xia, 2021;Secrest et al, 2021b), H o (Luongo et al, 2022;Dainotti et al, 2022), and galaxy shapes (Javanmardi and Kroupa, 2017).…”

Energy Based True Definition of Cosmic Red Shift and Quantum Halt of the Current Universe Having Light Speed Rotation

“…Cosmic isotropy and flatness (no curvature) are the rival factors that make cosmologists to ignore the idea of cosmic rotation. Isotropy point of view, many cosmologists [21,22] are analyzing the true nature of the assumed cosmic isotropy in all possible ways. Future observations may definitely shed light on the validity of Perfect Cosmological Principle i.e.…”

Loss of angular momentum when the planet’s atmosphere leaks into space

“…Note that the requirement for homogeneity, i.e. the similarity of different points in space is often called the Copernican principle, the principle of mediocrity, or the cosmological principle [10]. Considering it to be certainly true, one can erroneously attribute any deviations from the standard model to the action of anisotropy.…”