Wednesday, October 7, 2020

Another Cosmology Domain Problem With LambdaCDM

The LambdaCDM (LCDM) model (i.e. cosmological constant, cold dark matter model) a.k.a. the Standard Model of Cosmology had been used to fit all observational data at scales larger than galaxy clusters (i.e. large scale structure) with a minimal six parameters set based on observational data.

But LCDM has hit some problems in its own large scale structure domain after its stunning success at predicting the peaks in the Cosmic Background Radiation. One of the biggest problems is the 21cm background radiation data from the EDGES experiment that favors a no dark matter scenario at the end of the "radiation era" ca. 500,000 years after the Big Bang. Another is the "impossible early galaxy" problem. And then there is the problem that the kind of Cold Dark Matter that the model assumes isn't a good fit for galaxy and galaxy cluster observations.

A new paper has revealed a new and completely independent problem with it, data that contradicts the "Cosmological principle" which is "the notion that the spatial distribution of matter in the universe is homogeneous and isotropic when viewed on a large enough scale, since the forces are expected to act uniformly throughout the universe, and should, therefore, produce no observable irregularities in the large-scale structuring over the course of evolution of the matter field that was initially laid down by the Big Bang." 

At least five other observations of very large scale structures from 1991 to 2013 also cast doubt on the empirical accuracy of this principle. Three of them, and this new result, involve large quasar structures. The other two involve "great walls" of over dense matter at a large scale that is not evenly distributed across the sky.

The paper and its abstract are as follows:

A Test of the Cosmological Principle with Quasars

We study the large-scale anisotropy of the Universe by measuring the dipole in the angular distribution of a flux-limited, all-sky sample of 1.3 million quasars observed by the Wide-field Infrared Survey Explorer (WISE). This sample is derived from the new CatWISE2020 catalog, which contains deep photometric measurements at 3.4 and 4.6 um from the cryogenic, post-cryogenic, and reactivation phases of the WISE mission. While the direction of the dipole in the quasar sky is similar to that of the cosmic microwave background (CMB), its amplitude is over twice as large, rejecting the canonical, exclusively kinematic interpretation of the CMB dipole with a p-value of 10^{-4} (3.9 sigma), the highest significance achieved to date in such studies. Our results are in conflict with the cosmological principle, a foundational assumption of the concordance Lambda$CDM model.
Cite as:arXiv:2009.14826 [astro-ph.CO]

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