Model-independent cosmological inference after the DESI DR2 data with improved inverse distance ladder

TL;DR

This work addresses the H0 tension and potential hints of dynamical dark energy by developing a model-independent inverse distance ladder based on PAge and its MAPAge extension. By combining DESY5 and DESI DR2 BAO with cosmic chronometers and Type Ia SNe (PantheonPlus or DESY5), the authors infer H0 ≈ 67.9 with ~3-4% precision, consistent with Planck and mildly in tension with SH0ES. Mapping common dark-energy models into the PAge (p_age, η) plane reveals deviations from ΛCDM, with Bayesian evidence favoring the PAge model over ΛCDM for DESY5+DESI DR2+CC (ln B ≈ 9.17), and MAPAge providing broadly similar constraints. The results underscore the value of a model-independent expansion history in testing late-time cosmology and motivate further redshift-binned analyses and calibration to clarify the nature of any dynamical dark energy.

Abstract

Recently, the baryon acoustic oscillations (BAO) measurements from the DESI survey have suggested hints of dynamical dark energy, challenging the standard $Λ$CDM model. In this work, we adopt an improved inverse distance ladder approach based on the latest cosmological data to provide a model-independent perspective, employing a global parametrization based on cosmic age (PAge). Our analysis incorporates DESI DR2 BAO measurements, cosmic chronometer (CC) data, and type Ia supernovae (SNe) observations from either the DESY5 or PantheonPlus datasets. For the DESY5+DESI DR2+CC datasets, we obtain $H_0 = 67.91 \pm 2.33~\mathrm{km~s^{-1}~Mpc^{-1}}$. This value is consistent with the Planck 2018 result, while shows $2.0 σ$ tension with the SH0ES measurement. Furthermore, by mapping specific cosmological models into PAge approximation parameter space $(p_{\mathrm{age}}, η)$, our model-independent analysis reveals a notable deviation from the $Λ\mathrm{CDM}$ model, as indicated by the DESY5 and DESI DR2 datasets. Finally, DESY5+DESI DR2+CC datasets provide nearly decisive evidence favoring the PAge model over the standard $Λ\mathrm{CDM}$ model. These findings highlight the need for further investigation into the expansion history to better understand the deviations from the $Λ\mathrm{CDM}$ model.

Figures (6)

• Figure 1: Comparison of approximation accuracy for PAge (green dash-dotted), MAPAge (red dashed), Taylor expansion in $z$ (brown dotted), and $y$ (light beige), targeting the fiducial $w_0 w_a \mathrm{CDM}$ (black) model. The lower-right inset figure shows normalized Hubble parameter $H(z)/H(z)_{w_0w_a \mathrm{CDM}}$ up to $z\sim10^3$. We fix the parameters of the $w_0w_a\rm CDM$ model to DESI DR2 results: $\Omega_\mathrm{m}= 0.32, ~H_0=66.74 ~\mathrm{km~s^{-1}~Mpc^{-1}} ,~w_0=-0.75,~ w_a=-0.86$DESI:2025zgx.
• Figure 2: Constraints on the PAge model from DESY5+DESI DR2+CC (green), DESY5+SDSS+CC (blue, dotted), PantheonPlus+DESI DR2+CC (purple), and PantheonPlus+SDSS+CC (brown, dotted). Planck 2018 (pink) and SH0ES (grey) benchmarks are included to illustrate the $H_0$ tension both from the direct $H_0$ constraints and from those inferred via $M_\mathrm{B}$ and $r_\mathrm{d}$. The SH0ES-equivalent $r_\mathrm{d}$ and Planck-equivalent $M_\mathrm{B}$ are obtained by equating $H_0r_\mathrm{d}$ and $a_\mathrm{B}$, respectively. Four datasets are presented in the $M_{\mathrm{B}}$–$H_0$ plane to illustrate the shift in the intercept of the magnitude-redshift relation vividly.
• Figure 3: The constraints on $\eta$ and $p_\mathrm{age}$ in the PAge model obtained from DESY5+DESI DR2+CC (green), DESY5+SDSS+CC (blue), PantheonPlus+DESI DR2+CC (purple), and PantheonPlus+SDSS+CC (pink). The DESI DR2 and Planck 2018 results are introduced for comparison. Since $\Lambda \mathrm{CDM}$ lacks one parameter compared to the PAge model, it is mapped as a straight line in the parameter space.
• Figure 4: The BAO distance for the PAge (blue), $w_0w_a\mathrm{CDM}$ (green), and $w\mathrm{CDM}$ (orange) models in DESY5 + DESI DR2 + CC. These distances are normalized by the best-fit $\Lambda \mathrm{CDM}$ model (black) in DESY5+DESI+CC. The data of DESI (purple, filled) are drawn with error bars.
• Figure 5: The reconstructed BAO distance for the PAge (green), MAPAge (red), incorporating DESI DR2 data. The shaded bands denote the corresponding $1\sigma$ uncertainties.