Tests of Evolving Dark Energy with Geometric Probes of the Late Late-Time Universe (2509.26480v1)

Abstract: Recent results from the Dark Energy Spectroscopic Instrument (DESI) have shown a strong statistical preference for a time-evolving dark energy model over $\Lambda$CDM when combining BAO, CMB, and supernova (SN) data. We investigate the robustness of this conclusion by isolating geometric information in weak lensing measurements from the DES Year 3 survey and combining it with different datasets. We introduce a hyperparameter, $\Omega_{\rm m}^{\rm growth}$, to decouple the growth contribution from the lensing 2-point correlation and thus bypass the possible effect of the $\sigma_8$ tension in our analysis. We then combine with the late-time geometric probes provided by BAO and SN, along with CMB primary data. The preference for evolving dark energy is consistent with the DESI-DR2 findings: when combining BAO, primary CMB, and weak lensing data, the $w_0w_a$CDM is preferred at about the $3\sigma$ significance. However, when we add SN, the result is sensitive to the choice of data: if we leave out $z<0.1$ SN data in the analysis, as a test of the effect of inhomogeneous calibration, we obtain a statistical significance below $2\sigma$ for time evolving dark energy. Indeed, the high-z only SN data \textbf{lowers} the evidence for evolving dark energy in all the data combinations we have examined. This underscores the importance of improved SN samples at low redshift and of alternative data combinations. We show that cosmic shear measurements with LSST Year 1 data will provide comparable power to current SN data. We discuss other low-redshift probes provided by lensing and galaxy clustering to test for evolving dark energy.