Gravity modification theories seem to more easily solve the Hubble tension than alternative theories.
Fifth forces are ubiquitous in modified theories of gravity. In this paper, we analyze their effect on the Cepheid-calibrated cosmic distance ladder, specifically with respect to the inferred value of the Hubble constant (H0). We consider a variety of effective models where the strength, or amount of screening, of the fifth force is estimated using proxy fields related to the large-scale structure of the Universe. For all models considered, the local distance ladder and the Planck value for H0 agrees with a probability ≳20%, relieving the tension compared to the concordance model with data being excluded at 99% confidence. The alleviated discrepancy comes partially at the cost of an increased tension between distance estimates from Cepheids and the tip of the red-giant branch (TRGB). Demanding also that the consistency between Cepheid and TRGB distance estimates is not impaired, some fifth force models can still accommodate the data with a probability ≳20%. This provides incentive for more detailed investigations of fundamental theories on which the effective models are based, and their effect on the Hubble tension.
Marcus Högås, Edvard Mörtsell, "The Hubble tension and fifth forces: a cosmic screenplay" arXiv:2309.01744 (September 4, 2023).
3 comments:
Hum... Interesting. So a backward search saying that the solution should cause these effects. Now all you theorists, sharpen your pencils! How often does this sort of search work when compared to "do the math first" search?
Cheers,
Guy
In the context of the Sunny Vagnozzi paper, would this be early-time new physics?
Quoting from the OP paper: "In this paper, we explore an alternative approach based on fifth forces, first suggested in ref.[22]. A fifth force is the result of an extra degree of freedom and effectively leads to an increase in the gravitational force in certain environments, compared with the predictions of general relativity(GR). This can be modelled as an increase in the gravitational constant (G) compared with the Newtonian constant of gravitation (GN). If G>GN in galaxies hosting both TypeIa supernovae (SNIa) and Cepheids but G≃GN in anchor galaxies with direct distance measurements, the SH0ES H0 is biased to a high value. Thus, taking a fifth force into account can potentially harmonize the SH0ES value with Planck. In ref.[22],it was shown that an increase in G relative to GN by 5%–30% in the host galaxies can alleviate the tension. In that work, the derived value of the Hubble constant was estimated by an effective rescaling. In the present paper,we infer the value of H0 using a full statistical analysis.
We analyze three different models where the value of the fifth force is determined by the value of a phenomenological proxy related to the large-scale structure of the Universe. These are the externally sourced gravitational potential(Φ), the externally sourced acceleration(a), and the externally sourced curvature(K), described in more detail below."
So, this is a MOND-like fifth force, not really early-time new physics. The effect comes from bias in the late-time observations.
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