Cosmic chronometers, Pantheon+ supernovae, and quasars favor coasting cosmologies over the flat \(\Lambda\)CDM model

We test and compare coasting cosmological models with curvature parameters \({k=\left\{ -1,0,+1 \right\}}\) in \({H_0^2 c^{-2}}\) units and the flat \(\Lambda\)CDM model by fitting them to cosmic chronometers (CC), the Pantheon+ sample of type Ia supernovae (SNe), and standardized quasars (QSOs). We used the \texttt{emcee} code for fitting CC data, a custom Markov Chain Monte Carlo implementation for SNe and QSOs, and Anderson-Darling tests for normality on normalized residuals for model comparison. Best-fit parameters are presented, constrained by data within redshift ranges \(z\leq 2\) for CCs, \(z\leq 2.3\) for SNe, and \(z\leq 7.54\) for QSOs. Coasting models, particularly the flat coasting model, are generally favored over the flat \(\Lambda\)CDM model. The overfitting of the flat \(\Lambda\)CDM model to Pantheon+ SNe and the large intrinsic scatter in QSO data suggest a need to refine error estimates in these datasets. We also highlight the seemingly fine-tuned nature of either the CC data or \(\Omega_{\mathrm{m},0}\) in the flat \(\Lambda\)CDM model to an \({H_1=H_0}\) coincidence when fitting \({H(z)=H_1z+H_0}\), a natural feature of coasting models.