A comparison of Bayesian and frequentist confidence intervals in the presence of a late Universe degeneracy
Abstract Hubble tension is a problem in one-dimensional (1D) posteriors, since local $$H_0$$ H 0 determinations are only sensitive to a single parameter. Projected 1D posteriors for $$\Lambda $$ Λ CDM cosmological parameters become more non-Gaussian with increasing effective redshift when the model...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
SpringerOpen
2025-02-01
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| Series: | European Physical Journal C: Particles and Fields |
| Online Access: | https://doi.org/10.1140/epjc/s10052-024-13727-0 |
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| Summary: | Abstract Hubble tension is a problem in one-dimensional (1D) posteriors, since local $$H_0$$ H 0 determinations are only sensitive to a single parameter. Projected 1D posteriors for $$\Lambda $$ Λ CDM cosmological parameters become more non-Gaussian with increasing effective redshift when the model is fitted to redshift-binned data in the late Universe. We explain mathematically why this non-Gaussianity arises and show, using observational Hubble data (OHD), that Markov chain Monte Carlo (MCMC) marginalisation leads to 1D posteriors that fail to track the $$\chi ^2$$ χ 2 minimum at $$68\%$$ 68 % confidence level in high redshift bins. To gain a second perspective, we resort to profile likelihoods as a complementary technique. Doing so, we observe that $$z \gtrsim 1$$ z ≳ 1 cosmic chronometer (CC) data currently prefer a non-evolving (constant) Hubble parameter over a Planck- $$\Lambda $$ Λ CDM cosmology at $$\sim 2 \sigma $$ ∼ 2 σ . Within the Hubble tension debate, it is imperative that subsamples of data sets with differing redshifts yield similar $$H_0$$ H 0 values. In addition, we confirm that MCMC degeneracies observed in 2D posteriors are not due to curves of constant $$\chi ^2$$ χ 2 . Finally, on the assumption that the Planck- $$\Lambda $$ Λ CDM cosmological model is correct, using profile likelihoods we confirm a $$>2 \sigma $$ > 2 σ discrepancy with Planck- $$\Lambda $$ Λ CDM in a combination of CC and baryon acoustic oscillations (BAO) data beyond $$z \sim 1.5$$ z ∼ 1.5 . This confirms a discrepancy reported earlier with fresh methodology. |
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| ISSN: | 1434-6052 |