Cosmology intertwined: A review of the particle physics, astrophysics, and cosmology associated with the cosmological tensions and anomalies

Abstract

The standard Λ Cold Dark Matter (ΛCDM) cosmological model provides a good description of a wide range of astrophysical and cosmological data. However, there are a few big open questions that make the standard model look like an approximation to a more realistic scenario yet to be found. In this paper, we list a few important goals that need to be addressed in the next decade, taking into account the current discordances between the different cosmological probes, such as the disagreement in the value of the Hubble constant H0, the σ8–S8 tension, and other less statistically significant anomalies. While these discordances can still be in part the result of systematic errors, their persistence after several years of accurate analysis strongly hints at cracks in the standard cosmological scenario and the necessity for new physics or generalisations beyond the standard model. In this paper, we focus on the 5.0σ tension between the Planck CMB estimate of the Hubble constant H0 and the SH0ES collaboration measurements. After showing the H0 evaluations made from different teams using different methods and geometric calibrations, we list a few interesting new physics models that could alleviate this tension and discuss how the next decade's experiments will be crucial. Moreover, we focus on the tension of the Planck CMB data with weak lensing measurements and redshift surveys, about the value of the matter energy density Ωm, and the amplitude or rate of the growth of structure (σ8,fσ8). We list a few interesting models proposed for alleviating this tension, and we discuss the importance of trying to fit a full array of data with a single model and not just one parameter at a time. Additionally, we present a wide range of other less discussed anomalies at a statistical significance level lower than the H0–S8 tensions which may also constitute hints towards new physics, and we discuss possible generic theoretical approaches that can collectively explain the non-standard nature of these signals. Finally, we give an overview of upgraded experiments and next-generation space missions and facilities on Earth that will be of crucial importance to address all these open questions.

Keywords

Affiliated Institutions

• Université Paris Cité FR
• University of Wisconsin–Madison US
• Academy of Athens GR
• City University of New York US
• University of Manchester GB
• Sorbonne Université FR
• University of Ioannina GR
• Lehman College US
• American Museum of Natural History US
• Case Western Reserve University US
• Centre de Recherche Astrophysique de Lyon FR
• Istituto Nazionale di Fisica Nucleare, Sezione di Bologna IT
• Universidade de São Paulo BR
• Boston University US
• École Polytechnique Fédérale de Lausanne CH
• Université de Montpellier FR
• University of Copenhagen DK
• Stockholm University SE
• Heidelberg Institute for Theoretical Studies DE
• CEA Paris-Saclay FR
• University of Edinburgh GB
• University of the Western Cape ZA
• Istituto Nazionale di Fisica Nucleare, Sezione di Roma I IT
• Centre National de la Recherche Scientifique FR
• University of Bologna IT
• Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères FR
• Istanbul Technical University TR
• University of Münster DE
• Institut de Recherche sur les Lois Fondamentales de l'Univers FR
• Sapienza University of Rome IT
• Institut d'Astrophysique de Paris FR
• Imperial College London GB
• Universidade Federal do Rio Grande do Norte BR
• Royal Observatory GB
• Scuola Superiore Meridionale IT
• The Graduate Center, CUNY US
• Istituto Nazionale di Fisica Nucleare, Sezione di Napoli IT
• National Observatory of Athens GR
• Laboratoire AstroParticule et Cosmologie FR
• Laboratoire Univers et Particules de Montpellier FR
• Heidelberg University DE
• Université Paris Sciences et Lettres FR
• École Normale Supérieure - PSL FR
• University of Hull GB
• National Institute for Astrophysics IT
• Commissariat à l'Énergie Atomique et aux Énergies Alternatives FR

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