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The $\Lambda$CDM model provides a good fit to a large span of cosmological data but harbors areas of phenomenology. With the improvement of the number and the accuracy of observations, discrepancies among key cosmological parameters of the…

Cosmology and Nongalactic Astrophysics · Physics 2021-07-14 Eleonora Di Valentino , Olga Mena , Supriya Pan , Luca Visinelli , Weiqiang Yang , Alessandro Melchiorri , David F. Mota , Adam G. Riess , Joseph Silk

Recent observations have identified a significant 4.9$\sigma$ tension between the cosmic dipole inferred from galaxy number counts and that derived from the Cosmic Microwave Background (CMB), suggesting a potential deviation from the…

Cosmology and Nongalactic Astrophysics · Physics 2025-07-29 Ge Chen , Chengcheng Han , Linwei Qiu

We present the idea that replacing the cosmological constant $\Lambda$ in the $\Lambda$CDM model by a distribution of walls, with very low tension compared to what one would expect from new physics, could help explaining the tension in the…

Cosmology and Nongalactic Astrophysics · Physics 2024-06-13 Colin D. Froggatt , Holger Bech Nielsen

We present a Bayesian analysis of the Quaia sample of 1.3 million quasars as a test of the cosmological principle. This principle postulates that the universe is homogeneous and isotropic on sufficiently large scales, forming the basis of…

Cosmology and Nongalactic Astrophysics · Physics 2024-08-16 Vasudev Mittal , Oliver T. Oayda , Geraint F. Lewis

The mismatch between the locally measured expansion rate of the universe and the one inferred from the cosmic microwave background measurements by Planck in the context of the standard $\Lambda$CDM, known as the Hubble tension, has become…

Cosmology and Nongalactic Astrophysics · Physics 2021-06-11 Karsten Jedamzik , Levon Pogosian , Gong-Bo Zhao

The Standard Model of cosmology, $\Lambda$CDM, while enormously successful, is currently unable to account for several cosmological anomalies the most prominent of which are in the measurements of the Hubble parameter and $S_8$.…

Cosmology and Nongalactic Astrophysics · Physics 2025-03-14 Amin Aboubrahim , Pran Nath

Recent analyses of the cosmic microwave background (CMB) maps from the WMAP satellite have uncovered evidence for a hemispherical power anomaly, i.e. a dipole modulation of the CMB power spectrum at large angular scales with an amplitude of…

Cosmology and Nongalactic Astrophysics · Physics 2009-09-28 Christopher M. Hirata

The $\Lambda$ Cold Dark Matter model ($\Lambda$CDM) represents the current standard model in cosmology. Within this, there is a tension between the value of the Hubble constant, $H_0$, inferred from local distance indicators and the angular…

Cosmology and Nongalactic Astrophysics · Physics 2018-09-26 Edvard Mörtsell , Suhail Dhawan

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

The Hubble tension that the standard $\Lambda$CDM model is suffering from can be resolved with pre-recombination early dark energy. We present the first constraint on the tensor-to-scalar ratio $r$ in corresponding Hubble-tension-free…

Cosmology and Nongalactic Astrophysics · Physics 2022-09-07 Gen Ye , Yun-Song Piao

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…

Cosmology and Nongalactic Astrophysics · Physics 2023-08-16 Caroline Guandalin , Jade Piat , Chris Clarkson , Roy Maartens

Cosmological parameters are constrained by a wide variety of observations. We examine the concordance diagram for modern measurements of the Hubble constant, the shape parameter from large scale structure, the cluster baryon fraction, and…

Cosmology and Nongalactic Astrophysics · Physics 2024-01-22 Stacy McGaugh

Despite the great observational success of the standard cosmological model some discrepancies in the inferred parameter constraints have manifested among a number of cosmological data sets. These include a tension between the expansion rate…

Cosmology and Nongalactic Astrophysics · Physics 2021-05-05 Benjamin Bose , Lucas Lombriser

The discrepancy between the value of the Hubble constant $H_0$ in the late, local universe and the one obtained from the Planck collaboration representing an all-sky value for the early universe reached the 5-$\sigma$ level. Approaches to…

Cosmology and Nongalactic Astrophysics · Physics 2023-11-14 Jenny Wagner

We study the global agreement between the most recent observations of the Cosmic Microwave Background temperature and polarization anisotropies angular power spectra released by the Atacama Cosmology Telescope and the Planck satellite in…

Cosmology and Nongalactic Astrophysics · Physics 2023-02-02 Eleonora Di Valentino , William Giarè , Alessandro Melchiorri , Joseph Silk

A simple and minimal extension of the standard cosmological $\Lambda$CDM model in which dark matter experiences an additional long-range scalar interaction is demonstrated to alleviate the long lasting Hubble-tension while letting…

Cosmology and Nongalactic Astrophysics · Physics 2024-05-08 Cyril Pitrou , Jean-Philippe Uzan

We examine the recent proposal [1] that the anti-cross-correlation of the scalar and tensor primordial fluctuations reconciles the tension between BICEP2 and Planck observations. We show that unfortunately the contribution from the…

Cosmology and Nongalactic Astrophysics · Physics 2014-08-06 Razieh Emami , Hassan Firouzjahi , Yi Wang

Beyond-$\Lambda$CDM models have been proposed to address various shortcomings of the standard cosmological model, such as the ``Hubble tension.'' These models often have an impact on the discrepancy in the amplitude of matter clustering,…

Cosmology and Nongalactic Astrophysics · Physics 2024-05-17 Igor de O. C. Pedreira , Micol Benetti , Elisa G. M. Ferreira , Leila L. Graef , Laura Herold

Tensions between cosmological parameters derived through different channels can be a genuine signature of new physics that $\Lambda$CDM as the standard model is not able to reproduce, in particular in the missing consistency between…

Cosmology and Nongalactic Astrophysics · Physics 2025-02-20 Benedikt Schosser , Pedro Riba Mello , Miguel Quartin , Bjoern Malte Schaefer

We theoretically analyze the dipole anisotropy observed in the quasar distribution from the CatWISE2020 catalog. The catalog data shows a peak around $z\approx 1$, suggesting the presence of a large-scale dipole component. We explore the…

Cosmology and Nongalactic Astrophysics · Physics 2025-10-16 Gopal Kashyap , Naveen K. Singh , Pankaj Jain