早期与晚期：基于DESI DR2的暗能量对比研究
Early against Late: A contrast on dark energy in the light of DESI DR2
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México（墨西哥国立自治大学物理科学研究所）
- Instituto de Física, Universidad Nacional Autónoma de México（墨西哥国立自治大学物理研究所）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
该研究以DESI DR2数据为基础，通过贝叶斯模型对比发现，早期暗能量（EDE）被明确排除，晚期CPL模型中度不被支持，暗能量动力学的偏好受宇宙时期影响，贝叶斯证据可削弱相关偏好。
AI中文摘要：
近期暗能量光谱仪（DESI）重子声学振荡（BAO）测量结合Ia型超新星和宇宙微波背景（CMB）数据的研究发现，暗示$\boldsymbol{\rm \u039b CDM}$模型可能存在参数层面的偏差。然而参数排除未考虑先验体积惩罚，而贝叶斯证据揭示了早期与晚期动力学之间的显著二分性。为量化该效应，我们开展了明确考虑暗能量动力学宇宙学时期的贝叶斯模型比较，对比宇宙历史相反时期的两种方案：复合再电离前的早期暗能量（EDE）和晚期Chevallier–Polarski–Linder（CPL）模型，两者均以基准$\boldsymbol{\rm \u039b CDM}$模型为参照。我们在将学习到的调和平均估计器应用于CMB分析前，基于背景水平对其与$\boldsymbol{\rm \texttt{UltraNest}}$进行了验证。仅背景数据已不支持这两种扩展模型，得到$\boldsymbol{\rm \u039b CDM}$与EDE的对数贝叶斯因子$\boldsymbol{\rm \u212f B_{\u039b CDM,EDE} = 2.45 \u00b1 0.25}$，以及$\boldsymbol{\rm \u039b CDM}$与CPL的对数贝叶斯因子$\boldsymbol{\rm \u212f B_{\u039b CDM,CPL} = 3.45 \u00b1 0.24}$。加入CMB数据后结果更明确：EDE被明确排除（$\boldsymbol{\rm \u212f B_{\u039b CDM,EDE} = 12.44 \u00b1 0.05}$），其早期暗能量分数被约束为$\boldsymbol{\rm 10^3\\,\Omega_e^{EDE} = 2.0^{+0.6}_{-1.0}}$；而CPL仍被中度不支持（$\boldsymbol{\rm \u212f B_{\u039b CDM,CPL} = 2.33 \u00b1 0.06}$），尽管两种模型的二维参数后验均显示出与$\boldsymbol{\rm \u039b CDM}$的多$\boldsymbol{\rm \u03c3}$偏差。因此，贝叶斯证据削弱了已报道的暗能量动力学偏好，该影响取决于所涉及的宇宙时期，这一点由我们从后验样本重建的$\boldsymbol{\rm w_{de}(z)}$和$\boldsymbol{\rm \u03a9_{de}(z)}$函数得到了证实。
英文摘要：
Recent findings from Dark Energy Spectroscopic Instrument (DESI) Baryon Acoustic Oscillation (BAO) measurements, combined with Type Ia supernovae and Cosmic Microwave Background (CMB) data, suggest potential parameter-level deviations from $Λ\text{CDM}$. However, parameter exclusions omit prior-volume penalties, whereas Bayesian evidence uncovers a stark dichotomy between early- and late-time dynamics. To quantify this effect, we perform a Bayesian model comparison that explicitly accounts for the cosmological epoch of dark energy dynamics, contrasting two schemes acting in opposite epochs of cosmic history: pre-recombination Early Dark Energy (EDE) and late-time Chevallier--Polarski--Linder (CPL), both measured against a baseline $Λ$CDM. We validate the learned harmonic-mean estimator against UltraNest (at background level) before applying it to the CMB analysis. Background-only data already disfavor both extensions, yielding {$\ln B_{Λ\text{CDM},\text{EDE}} = 1.48 \pm 0.18$ and $\ln B_{Λ\text{CDM},\text{CPL}} = 2.36 \pm 0.24$}. Including CMB sharpens this result: {EDE is very strongly rejected ($\ln B_{Λ\text{CDM},\text{EDE}} \approx 12.61 \pm 0.17$)} with its early-time fraction constrained to $10^3\,Ω_e^{\rm EDE} = 2.0^{+0.6}_{-1.0}$, whereas CPL remains only mildly disfavored ($\ln B_{Λ\text{CDM},\text{CPL}} \approx 2.34 \pm 0.18$), even though 2D parameter posteriors for both models display a multi-$σ$ deviation from $Λ\text{CDM}$. Thus, Bayesian evidence weakens reported preferences for dark energy dynamics, with the impact depending on the cosmic epoch involved, confirmed by our functional reconstructions of $w_{\rm de}(z)$ and $Ω_{\rm de}(z)$ from posterior samples.
