paper

Probing Time-Varying Dark Energy with DESI: The Crucial Role of Precision Matter Density (Ω_{m0}) Measurements

arXiv:2505.19052 · doi:10.1140/epjc/s10052-026-15541-2

Abstract

Accurate measurements of fundamental cosmological parameters, especially the Hubble constant (H_0) and present-day matter density (Ω_{m0}), are crucial for constraining dark energy (DE) evolution. We analyze the sensitivities of cosmological observables (H(z), D_L(z), E_{G}) to Ω_{m0}, w_0, and w_an under different parametrizations. Our results show observables are far more sensitive to Ω_{m0} than to DE equation of state parameters (e.g., at z \sim 0.5, H(z)'s Ω_{m0} sensitivity is \sim 0.7 vs. w_a's \sim 0.04). This hierarchy mandates high-precision Ω_{m0} measurements to accurately constrain time-varying DE. We also find DE parameter sensitivity highly depends on parametrization; the standard CPL form shows low sensitivity to w_a, but ω(z) = w_0 + w_a \ln(1+z) significantly enhances it. Our analysis of DESI DR1/DR2 data confirms these theoretical limits: standalone DESI data primarily provides only upper limits for w_a, underscoring insufficient constraining power for a definitive time-varying DE detection. While combined datasets offer tighter constraints, interpretation requires caution due to parametrization influence. We further confirm this point using simulated Supernovae MCMC data. In conclusion, improving Ω_{m0} precision and adopting optimized parametrizations are imperative for future surveys like DESI to fully probe dark energy's nature.

arXiv comment31 pages, 8 figures, Final version accepted for publication in The European Physical Journal C

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