A hint of matter underdensity at low $z$?

Abstract

The $\Lambda$CDM cosmological model provides to first approximation a good description of the universe, but various tensions with data, most notably Hubble tension, persist. In this work we confront $\Lambda$CDM with the Pantheon Type Ia supernovae dataset and perform a two-parameter fit of the distance modulus for a running cut-off $z_{\text{max}}$. We observe that in a window between $z_{\text{max}}\approx 0.1$ and $z_{\text{max}}\approx 0.16$ there is a 1 - 2 $\sigma$ discrepancy with the Planck value ${\omega }_m=0.315\pm 0.007$, which points to a potential matter underdensity. For high-energy theorists, the analysis appears to support the de Sitter Swampland conjecture.

9 pages, my first foray into astro-ph, feedback welcome; v2 11 pages, analysis improved, references updated; v3 corrections to statistical significance, version to appear in JCAP

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• Interacting dark energy in the early 2020s: a promising solution to the $H_0$ and cosmic shear tensions
• Running Hubble Tension and a H0 Diagnostic
• From galactic bars to the Hubble tension: weighing up the astrophysical evidence for Milgromian gravity
• The KBC void and Hubble tension contradict $\Lambda$CDM on a Gpc scale $-$ Milgromian dynamics as a possible solution
• A new method to build the (inverse) distance ladder
• Cosmography and flat $\Lambda$CDM tensions at high redshift
• Hubble tension or a transition of the Cepheid SnIa calibrator parameters?
• Hints of a Local Matter Underdensity or Modified Gravity in the Low $z$ Pantheon data
• On the homogeneity of SnIa absolute magnitude in the Pantheon+ sample
• A Critique of Holographic Dark Energy
• Resolving the $H_0$ tension with diffusion
• Inference of the cosmic rest-frame from supernovae Ia
• Cosmology With Low-Redshift Observations: No Signal For New Physics
• The Copernican principle in light of the latest cosmological data
• Multi-field Inflation in High-Slope Potentials
• Testing $\Lambda$CDM cosmology in a binned universe: anomalies in the deceleration parameter
• Bulk Flow Motion Detection in the Local Universe with Pantheon$+$ Type Ia Supernovae
• Constraining Dark-Matter Ensembles with Supernova Data
• Charged Dark Matter and the $H_0$ tension
• Is gravity getting weaker at low z? Observational evidence and theoretical implications
• Hitchhiker's Guide to the Swampland: The Cosmologist's Handbook to the string-theoretical Swampland Programme
• Viability tests of \textit{f(R)}-gravity models with Supernovae Type 1A data