Cosmology 2025 @ Elba Island

Addressing the Hubble tension and a proposal to increase the accuracy of cosmological observables

11 Sept 2025, 17:30

30m

Hermitage Hotel, Isola D'Elba

Talk The current Cosmological Model and its Tensions (Theory and observations) Afternoon session

Speaker

Horst Foidl (Department of Astrophysics at the University of Vienna)

Description

The Hubble tension denotes the discrepant values of $H_0$ obtained from direct measurements in the local Universe compared to those derived from the CMB. Observational programs often compare their data also with extensions to ΛCDM applying dynamical models of dark energy (DDE) with a time-dependent equation of state parameter w. They use the MCMC method to fit the ΛCDM extensions to their data, where they use the CPL model $w(a) = w_0 + w_a(1 − a)$ as the parametrization of the DDE model. We discovered a degeneracy in the MCMC method and propose a complementary computational procedure as an extension to the MCMC method that breaks the degeneracy, where our results reveal that the CPL model $w(a) = −0.9 + 0.1(1 − a)$ could provide a resolution to the Hubble tension problem. Moreover, we find that this approach can serve as a kind of consistency check for cosmological models and will increase the accuracy of inferred cosmological parameters significantly, in particular for ΛCDM extensions with DDE.

Presentation materials

Cosmo2025-Hubble tension and a increasing the accuracy of cosmological observables-Foidl.pdf