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Crisis for cosmology?

22 January 2020
Detail of the CMB anisotropy
Detail of the CMB anisotropy. Credit: ESA/Planck Legacy 2018

Planck data on the cosmic microwave background (CMB) have been reinterpreted to favour a closed universe at more than 99% confidence, in contradiction with the flat universe favoured by the established ΛCDM model of cosmology. In their new fit to Planck’s 2018 data release, Eleonora Di Valentino (Manchester), Alessandro Melchiorri (La Sapienza) and Joe Silk (Oxford) exchanged an anomalously large lensing amplitude (a phenomenological parameter that rescales the gravitational-lensing potential in the CMB power spectrum) for a higher energy density.

In addition to the lensing anomaly, which leads to inconsistencies between large and small scales, the flat interpretation is already plagued by a 4.4σ tension with the latest determination of the Hubble constant using observations of the recession of Cepheid stars – a tension that grows to 5.4σ in a closed universe.

The inconsistencies between data sets signal “a possible crisis for cosmology”, argue the authors.

Further reading

E. Di Valentino et al. 2019 Nat. Astron./arXiv:1911.02087

A. Riess et al. 2019 arXiv:1903.07603

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