AI 中文总结
该研究将最优红移形式体系应用于宇宙学数据集，发现CPL状态方程的phantom穿越具有3.01-3.55σ的显著性，验证了动力学暗能量的phantom行为。
AI 中文摘要
DESI及其他宇宙学数据集的最新结果表明，宇宙学更倾向于动力学暗能量，其具有随时间演化的状态方程（EOS）$w(z)$。此外，使用CPL参数化的分析显示，该状态方程存在$w(z)=-1$线的phantom穿越。在姊妹论文I中，我们假设了CPL参数化及其推广形式，引入了最优标度因子（或红移）的形式体系，该量旨在同时最大化其与宇宙学常数取值-1的距离，并最小化EOS的不确定性，从而在给定数据集组合下，最大化该特定红移处与宇宙学常数的张力。在本论文II中，我们将最优红移形式体系应用于现有的重子声学振荡、宇宙微波背景及超新星数据集组合，特别关注CPL框架内的phantom线穿越。鉴于此前对phantom线下方区域EOS约束的显著性相对较低，我们计算了多种数据集组合的最优红移，以识别那些能在穿越点前后最好地约束$w(z)$偏离-1的情况。我们发现，在穿越点前，存在数据集组合及对应最优红移，使得$w(z)$位于-1线下方，新的显著性水平达到3.01至3.22σ；在穿越点后，$w(z)$位于-1线上方，显著性水平为3.30至3.55σ。本研究的重点是应用这一新框架，利用现有数据集最大化CPL框架内phantom穿越信号的显著性。确定该穿越是有效还是内在的，并识别潜在的微观物理模型，是与本研究目标不同的独立问题，仍是未来研究的重要方向，我们的发现进一步推动了这些方向的研究。（内容有删节）
英文摘要
Recent results from DESI and other cosmological datasets have indicated a preference for dynamical dark energy, with a time-evolving equation of state (EOS), $w(z)$. Furthermore, analyses using the CPL parameterization give an EOS with a phantom crossing of the $w(z)=-1$ line. In a companion paper-I, we assumed the CPL parameterization and its generalization, and introduced the formalism of the optimal scale factor (or redshift), a quantity designed to simultaneously maximize the distance from the cosmological constant value of $-1$ and to minimize the uncertainty on the EOS, thereby maximizing the tension with the cosmological constant at that specific redshift for a given dataset combination. In this paper-II, we apply the optimal-redshift formalism to available baryon acoustic oscillation, Cosmic Microwave Background, and supernova dataset combinations, with a particular focus on the phantom-line crossing within CPL. Motivated by the relatively low significance of previous constraints on the EOS in the region below the phantom line, we calculate the optimal redshift for a variety of dataset combinations to identify those that best constrain departures from $w(z)=-1$ before and after the crossing. We find combinations and corresponding optimal redshifts for which $w(z)$ lies below the ``$-1$'' line with new significance levels reaching $3.01$--$3.22σ$ before the crossing point, and $3.30$--$3.55σ$ above ``$-1$" after the crossing. Our focus in this work is the application of a new framework that maximizes the significance of the phantom-crossing signal within CPL using currently available datasets. Determining whether this crossing is effective or intrinsic, and identifying the underlying microphysical models, constitute separate questions from the aim of the present work and remain important directions for future investigation, further motivated by our findings. Abridged.
Comments19 pages, 6 figures
