A Snowmass 2021 contribution reminds us that there are severe tensions in LambdaCDM parameters that threaten the model itself.
In this paper we will list a few important goals that need to be addressed in the next decade, also taking into account the current discordances between the different cosmological probes, such as the disagreement in the value of the Hubble constant H(0), the σ8 -- S8 tension, and other less statistically significant anomalies.
While these discordances can still be in part the result of systematic errors, their persistence after several years of accurate analysis strongly hints at cracks in the standard cosmological scenario and the necessity for new physics or generalisations beyond the standard model.
In this paper, we focus on the 5.0σ tension between the Planck CMB estimate of the Hubble constant H(0) and the SH0ES collaboration measurements.
After showing the H(0) evaluations made from different teams using different methods and geometric calibrations, we list a few interesting new physics models that could alleviate this tension and discuss how the next decade's experiments will be crucial.
Moreover, we focus on the tension of the Planck CMB data with weak lensing measurements and redshift surveys, about the value of the matter energy density Ω(m), and the amplitude or rate of the growth of structure (σ8, f σ8).
We list a few interesting models proposed for alleviating this tension, and we discuss the importance of trying to fit a full array of data with a single model and not just one parameter at a time. Additionally, we present a wide range of other less discussed anomalies at a statistical significance level lower than the H(0) -- S8 tensions which may also constitute hints towards new physics, and we discuss possible generic theoretical approaches that can collectively explain the non-standard nature of these signals.
Elcio Abdalla, et al., "Cosmology Intertwined: A Review of the Particle Physics, Astrophysics, and Cosmology Associated with the Cosmological Tensions and Anomalies" arXiv:2203.06142 (March 11, 2022).
btw
ReplyDeletecould you read then blog and how it fits in with Deur
The origin of the MOND critical acceleration scale
David Roscoe
There is a link: if the idea of a quasi-fractal D≈2 universe on medium scales is taken seriously then there is an associated characteristic mass surface density scale, ΣF say, and an associated characteristic gravitational acceleration scale, aF=4πGΣF. If, furthermore, the quasi-fractal structure is taken to include the inter-galactic medium, then it is an obvious step to consider the possibility that a0 and aF are the same thing.
Since the scaling relationship also gives rise to the Baryonic Tully-Fisher Relationship, but with a0 replaced by aF, we are led unambiguously to the conclusion that a0 and aF are, in reality, one and the same thing.
arXiv:2111.01700
based on this
Gravitational force distribution in fractal structures
A. Gabrielli, F. Sylos Labini, S. Pellegrini
and
Fractal Analysis of the UltraVISTA Galaxy Survey
Sharon Teles (1), Amanda R. Lopes (2), Marcelo B. Ribeiro (1,3) ((1) Valongo Observatory, Universidade Federal do Rio de Janeiro, Brazil, (2) Department of Astronomy, Observatório Nacional, Rio de Janeiro, Brazil, (3) Physics Institute, Universidade Federal do Rio de Janeiro, Brazil)
This paper seeks to test if the large-scale galaxy distribution can be characterized as a fractal system.