Constraints on AvERA Cosmologies from Cosmic Chronometers and Type Ia Supernovae

Abstract

We constrain AvERA cosmologies in comparison with the flat $\Lambda$CDM model using cosmic chronometer (CC) data and the Pantheon+ sample of type Ia supernovae (SNe Ia). The analysis includes fits to both CC and SN datasets using the \texttt{dynesty} dynamic nested sampling algorithm. For model comparison, we use the Bayesian model evidences and Anderson-Darling tests applied to the normalized residuals to assess consistency with a standard normal distribution. Best-fit parameters are derived within the redshift ranges $z\le 2$ for CCs and $z\le 2.3$ for SNe. For the baseline AvERA cosmology, we obtain best-fit values of the Hubble constant of $H_0=68.32_{-3.27}^{+3.21}\mathrm{km}{\mathrm{s}}^{-1}\mathrm{Mp}{\mathrm{c}}^{-1}$ from the CC analysis and $H_0=71.99_{-1.03}^{+1.05}\mathrm{km}{\mathrm{s}}^{-1}\mathrm{Mp}{\mathrm{c}}^{-1}$ from the SN analysis, each consistent within $1\sigma$ with the corresponding AvERA simulation value of $H(z=0)$. While both the CC and SN datasets yield higher Bayesian evidence for the flat $\Lambda$CDM model, they favor the AvERA cosmologies according to the Anderson-Darling test. We have identified signs of overfitting in each model, which suggests the possibility of overestimating the uncertainties in the Pantheon+ covariance matrix.

7 pages, 3 figures

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