基于DESI BAO结合Ia型超新星与宇宙微波背景重新审视暗能量的状态方程
Revisiting the equation of state of dark energy from DESI BAO with SNe Ia and CMB
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中文总结 AI 辅助
本文结合DESI BAO DR2、Pantheon+ SNe Ia与Planck 2018 CMB数据，采用红移截断策略分析w0waCDM模型，发现z~0.4-0.8数据会致约2σ偏差，无可靠证据支持其优于ΛCDM模型，偏差或源于统计波动与子样本局限。
中文摘要 AI 辅助
暗能量光谱仪（DESI）的重子声学振荡（BAO）测量近期显示，相对于标准ΛCDM模型，存在对动力学暗能量的微弱偏好。本文使用DESI BAO DR2、Pantheon+ Ia型超新星（SNe Ia）以及普朗克2018年宇宙微波背景（CMB）距离先验数据，对w0waCDM模型进行分析。为探究不同数据部分如何影响与ΛCDM模型的表观偏差，本文采用两种互补的红移截断策略，将数据集划分为z<zcut和z>zcut两个子样本。研究发现，当包含红移范围z~0.4-0.8的BAO与SNe Ia数据时，出现最显著的参数偏移，显著性约为2σ；在该框架内，加入更高红移的测量值会逐渐削弱这一偏差，使约束结果更接近ΛCDM的预期。此外，信息准则显示，w0waCDM模型与ΛCDM模型之间无统计学显著偏好，而贝叶斯信息准则始终倾向于ΛCDM模型。同时，参数偏移一致性检验表明，互补红移子样本之间不存在统计学显著张力。在本文采用的DESI BAO DR2、Pantheon+及CMB距离先验框架下，上述结果未提供统计学上可靠的证据支持w0waCDM模型优于ΛCDM模型，反而表明不同红移截断下的表观参数偏移可能受统计波动及当前子样本有限的精度与数据点数量影响。本文的分析为评估不同红移选择下宇宙学约束的推断变化提供了一种互补的红移相关诊断方法。
英文摘要
The Dark Energy Spectroscopic Instrument (DESI) measurements of baryon acoustic oscillations (BAO) have recently shown a mild preference for dynamical dark energy over the standard $\rm Λ$CDM model. In this paper, we analyze the $w_0w_a$CDM model using DESI BAO DR2, Pantheon+ SNe Ia, and Planck 2018 CMB distance prior data. To examine how different parts of the data affect the apparent deviation from $\rm Λ$CDM, we adopt two complementary redshift-cut strategies, dividing the dataset into $z<z_{\rm cut}$ and $z>z_{\rm cut}$ subsamples. We find that the most noticeable shifts occur when BAO and SNe Ia data in the redshift range $z\sim0.4$--$0.8$ are included, reaching a significance of about $\sim2σ$. Within this framework, the inclusion of higher-redshift measurements progressively weakens this deviation and brings the constraints closer to the $\rm Λ$CDM expectation. Moreover, the information criteria show no statistically significant preference between the $w_0w_a$CDM and $\rm Λ$CDM models, while the Bayesian information criterion consistently favors the $\rm Λ$CDM model. In addition, a parameter-shift consistency test reveals no statistically significant tension between complementary redshift subsamples. Within the DESI BAO DR2, Pantheon+, and CMB distance prior framework adopted here, these results do not provide statistically robust evidence favoring the $w_0w_a$CDM model over $\rm Λ$CDM. They instead indicate that the apparent parameter shifts under different redshift cuts may be affected by statistical fluctuations and by the limited precision and number of datapoints in the current subsamples. Our analysis provides a complementary redshift-dependent diagnostic for assessing how the inferred cosmological constraints vary under different redshift selections.
