Hubble tension: Showing the cracks in Gaussian Processes

Date:
November 15, 2021
Source:
Springer
Summary:
A new analysis of the Hubble constant to show that the Gaussian
Processes data reconstruction technique may not actually be
independent of all cosmological models -- and that it may be time
to question the validity of model independence itself.



FULL STORY ==========================================================================
The technique of Gaussian Processes (GP) is widely used to reconstruct cosmological parameters, most notably the expansion rate of the universe,
using observational data. For many cosmologists, the crowning achievement
of this approach is its 'model independence' -- meaning it can be applied universally across all models. Through new analysis published inEPJ
C, Eoin O' Colga'in at Sogang University, Seoul, and Mohammad Mehdi Sheikh-Jabbari at IPM, Tehran, use the Hubble constant (H0) to show
that this may not be the case -- and that it may be time to question
the validity of model independence itself.


==========================================================================
The duo's results could have profound implications for the methods
cosmologists use to study the universe. As they construct their models,
these researchers must make assumptions about certain parameters which
they can't possibly know everything about. Inevitably, their differing assumptions lead to contradictions between models -- which in turn,
can seed new progress towards better cosmological descriptions. Around
20 years ago, this led to the 'LCDM' model: which in its current form,
can account for the universe's accelerating expansion. Inevitably,
however, the LCDM model soon created new tensions in other areas. The
GP data reconstruction approach has recently emerged in the face of
these conflicts; and thanks to the widespread assumption of its model- independence, it has now become a centrally important tool in cosmology.

In their study, O' Colga'in and Sheikh-Jabbari evaluated GP using H0:
a value defining the relationship between galaxies' distances from us,
and speeds at which they move away from us. Within extensive data gathered
so far, a mismatch has emerged between smaller-scale measurements of H0,
and its overall value, measured across the entire sky. Through their
analysis, the duo concluded that the model-independent statement of
this 'Hubble tension,' which is partly based on GP analysis methods,
is a misnomer. Going further, they suggest that 'model independence'
itself is an outdated concept in the era of `precision cosmology',
as it typically underestimate the errors on parameters.

========================================================================== Story Source: Materials provided by Springer. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Eoin O' Colga'in, M. M. Sheikh-Jabbari. Elucidating cosmological
model
dependence with $$H_0$$. The European Physical Journal C, 2021;
81 (10) DOI: 10.1140/epjc/s10052-021-09708-2 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211115123445.htm

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