涌现暗能量中的亚稳态：一个面对宇宙学观测的新框架
Metastability in Emergent Dark Energy: A New Framework Confronting Cosmological Observations
AI总结：
提出亚稳态涌现暗能量（MEDE）模型，通过双曲正切暗能量状态方程引入两个自由参数，利用Planck CMB、DESI DR2 BAO和Ia型超新星数据约束，发现与宇宙学常数的显著偏离，且模型优于ΛCDM。
摘要：
我们提出了亚稳态涌现暗能量（MEDE）模型，这是对现象学涌现暗能量（PEDE）和广义涌现暗能量（GEDE）框架的一种新颖的现象学扩展，其中暗能量表现出过渡行为，在晚期出现并朝向未来消失。该模型自然地实现了暗能量状态方程中幻影分界线的平滑穿越，正如近期观测所暗示的那样。MEDE模型由双曲正切暗能量状态方程$w(z)=-1-Δ anh[\log_{10}((1+z)/(1+z_t))]$定义，仅引入两个自由参数：跃迁红移$z_t$和变化幅度$Δ$，同时允许暗能量的涌现和过渡行为。我们使用Planck CMB、DESI DR2 BAO以及不同Ia型超新星汇编数据的联合数据集对MEDE模型进行约束，得到$z_t=0.425^{+0.084}_{-0.120}$和$Δ=0.87^{+0.29}_{-0.35}$（对于CMB+DESI+PantheonPlus），表明与宇宙学常数存在统计显著的偏离。统计比较显示，MEDE模型被联合数据集优先于ΛCDM，$Δ\rm DIC_{ MEDE-ΛCDM}= -9.29$。MEDE模型的表现与CPL动力学暗能量参数化相当（$Δ\rm DIC_{MEDE-CPL} = 0.74$），使用当前数据与CPL没有强烈的统计区别。值得注意的是，MEDE保留了ΛCDM在描述早期宇宙物理方面的成功，并自然地容纳了最新低红移观测所暗示的幻影穿越特征。MEDE情景提供了一种引人注目的暗能量现象学，可能引导我们走向有趣的理论启示。
英文摘要：
We propose the Metastable Emergent Dark Energy (MEDE) model, a novel phenomenological extension of the Phenomenological (PEDE) and Generalized (GEDE) Emergent Dark Energy frameworks, in which dark energy exhibits a transitionary behavior, appearing at late times and vanishing toward the future. This model naturally enables a smooth crossing of the phantom divide line in the dark energy equation of state, as hinted at by recent observations. The MEDE model is defined by a hyperbolic tangent dark energy equation of state $w(z)=-1-Δ\tanh[\log_{10}((1+z)/(1+z_t))]$, introducing only two free parameters, the transition redshift $z_t$ and the variation amplitude $Δ$, allowing both the emergent and transitionary behavior of dark energy. We constrain the MEDE model using a combined dataset of Planck CMB, DESI DR2 BAO, and different compilations of Type Ia supernovae, obtaining $z_t=0.425^{+0.084}_{-0.120}$ and $Δ=0.87^{+0.29}_{-0.35}$ (for CMB+DESI+PantheonPlus), indicating a statistically significant deviation from the cosmological constant. Statistical comparisons show that the MEDE model is preferred over $Λ$CDM by the combined dataset, with $Δ\rm DIC_{ MEDE-ΛCDM}= -9.29$. The MEDE model performs comparably to the CPL dynamical dark energy parametrization ($Δ\rm DIC_{MEDE-CPL} = 0.74$), with no strong statistical distinction from CPL using current data. Notably, MEDE preserves the success of $Λ$CDM in describing early-universe physics and naturally accommodates the phantom-crossing signature indicated by the latest low-redshift observations. The MEDE scenario provides a compelling dark energy phenomenology that may guide us toward interesting theoretical implications.
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