Consequences of using a smooth cosmic distance in a lumpy universe. I.
Abstract
How do we appropriately fit a model based on an idealized FriedmannLemaître RobertsonWalker spacetime to observations made from a single location in a lumpy universe? We address this question for surveys that measure the imprints of the baryon acoustic oscillation in galaxy distribution and the peak apparent magnitude of the type 1A supernova. These observables are related to the cosmological model through the AlcockPaczyński parameters and the distanceredshift relation. Using the corresponding inhomogeneous spacetime expressions of these as observed data, we perform a parameter inference assuming that the background FriedmannLemaître RobertsonWalker model is the correct model of the Universe. This process allows us to estimate the best fit Hubble rate and the deceleration parameter. We find that the inferred Hubble rate from the monopole of the AlcockPaczyński parameters is in tension with the Hubble rate determined using the distanceredshift relation. The latter gives the best fit Hubble rate for the cosmological expansion. The constraint on the Hubble rate from the AlcockPaczyński parameters is contaminated by the environment. When the environmental contribution is restricted to modes in the Hubble flow, we find about (912)% discrepancy in the Hubble rate. Finally, we comment on the insufficiency of the method of cosmography in constraining the deceleration parameter.
 Publication:

Physical Review D
 Pub Date:
 July 2022
 DOI:
 10.1103/PhysRevD.106.023514
 arXiv:
 arXiv:2202.08230
 Bibcode:
 2022PhRvD.106b3514U
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics;
 General Relativity and Quantum Cosmology
 EPrint:
 Accepted for publication by PRD