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The art of building a smooth cosmic distance ladder in a perturbed universe

Obinna Umeh
ICG, University of Portsmouth, UK

How does a smooth cosmic distance ladder emerge from observations made from a single location in a lumpy Universe? Distances to the Type Ia supernova (SNIa) in the Hubble flow are anchored on local distance measurements to sources that are very nearby. We described how this configuration could be built in a perturbed universe where lumpiness is described as small perturbations on top of a flat Friedmann-Lemaître Robertson-Walker (FLRW) spacetime. We show that there is a non-negligible modification (about 11%) to the background FLRW area distance due to the presence of inhomogeneities in the immediate neighbourhood of an observer. We find that the modification is sourced by the electric part of the Weyl tensor indicating a tidal deformation of the local spacetime of the observer. We show in detail how it could impact the calibration of the SNIa absolute magnitude in the Hubble flow. We show that it resolves the SNIa absolute magnitude and Hubble tensions simultaneously without the need for early or late dark energy.

2022 May 09, 16:30

Online broadcast (Zoom)

Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia