Abstract
Abstract Current cosmological observations point to a serious discrepancy between the observed Hubble parameter obtained using direct versus cosmic microwave background radiation measurements. Besides this so-called Hubble–Lemaître tension, we also find considerable evidence in diverse cosmological observables that indicate violation of the cosmological principle. In this paper, we suggest that both these discrepancies are related and can be explained by invoking superhorizon perturbations in the universe. We implement this by considering a single superhorizon mode and showing that it leads to both a dipole in large-scale structures and a shift in the Hubble–Lemaître parameter. Furthermore, the shift is found to be independent of redshift up to a certain distance. This is nicely consistent with the data.
Highlights
Around 90 years ago, Georges Henri Joseph Edouard Lemaıtre proposed that an expanding universe can explain the recession of nearby galaxies [1]
They find that a superhorizon mode, for a range of α, κ values, can consistently explain both the CMB and NRAO VLA Sky Survey (NVSS) observations while remaining in harmony with others, viz., the dipole anisotropy in local Hubble–Lemaıtre parameter measurements and local bulk flow observations
We have shown that both of these can be explained within the framework of a phenomenological model that assumes the existence of a superhorizon mode in the Universe
Summary
Around 90 years ago, Georges Henri Joseph Edouard Lemaıtre proposed that an expanding universe can explain the recession of nearby galaxies [1]. It provides a good fit to a large number of cosmological observations, such as the CMB radiation, primordial helium abundance, baryonic acoustic oscillations (BAO), galaxy clustering, Hubble parameter measurements etc Inspite of all these successes, there have been several different observations showing significant tension with the standard ΛCDM. Over the decades and to ever increasing distances, a variety of probes like SNIa standard candles [37–41], improved stellar/Cepheid distance indicators [42] etc., have been deployed to achieve this These advancements have made the directly measured value of the Hubble parameter extremely accurate — from Hubble’s value of H0 = 500 km s−1 Mpc−1 to the present value H0 = 73± ∼ 2 km s−1 Mpc−1. We propose a novel and elegant solution to both problems with a minimal modification of the ΛCDM model
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