Planck evidence for a closed Universe and a possible crisis for cosmology

• DOI: 10.1038/s41550-019-0906-9
• Publication Date: 2019-11-04T17:04:07Z
• Authors: Eleonora Di Valen...; Alessandro Melchi...; Joseph Silk
• Keywords: Cold dark matter; Planck length; Cosmological constant; Cosmic background radiation; Observable universe; Particle horizon; Phantom energy; Baryon Acoustic Oscillations; Planck energy

The recent Planck Legacy 2018 release has confirmed the presence of an enhanced lensing amplitude in CMB power spectra compared to that predicted in the standard $��$CDM model. A closed universe can provide a physical explanation for this effect, with the Planck CMB spectra now preferring a positive curvature at more than $99 \%$ C.L. Here we further investigate the evidence for a closed universe from Planck, showing that positive curvature naturally explains the anomalous lensing amplitude and demonstrating that it also removes a well-known tension within the Planck data set concerning the values of cosmological parameters derived at different angular scales. We show that since the Planck power spectra prefer a closed universe, discordances higher than generally estimated arise for most of the local cosmological observables, including BAO. The assumption of a flat universe could, therefore, mask a cosmological crisis where disparate observed properties of the Universe appear to be mutually inconsistent. Future measurements are needed to clarify whether the observed discordances are due to undetected systematics, or to new physics, or simply are a statistical fluctuation.<br/>35 pages, 8 figures<br/>