AI 中文总结
研究通过ΛXCDM模型拟合多组宇宙学数据，发现其能自然穿越幽灵分界线，宇宙子X表现特殊，该模型比w0waCDM拟合更好且缓解宇宙巧合问题，有望从第一原理解释幽灵分界线穿越，为暗能量相关观测提供理论支持。
AI 中文摘要
复合动力学暗能量（DDE）最近被视为一种通过所谓的wXCDM模型来缓解宇宙学张力的有效方式，它是ΛXCDM模型的简化版。ΛXCDM是一种复合可变真空模型（RVM），包含一般性质的暗能量成分X（“宇宙子”）。我们计算了ΛXCDM的有效状态方程，并使用先进技术将该模型与两组标准宇宙学数据进行拟合，包括潘特heon +的超新星Ia数据、DES - Dovekie的超新星Ia数据、DESI DR2的重子声学振荡数据以及普朗克PR4的宇宙微波背景数据。我们发现，ΛXCDM自然地实现了幽灵分界线的穿越，宇宙子X在当前附近表现为“幽灵物质”，满足强能量条件且提供正压力。ΛXCDM比w0waCDM拟合得更好，还缓解了宇宙巧合问题，有望从第一原理解释幽灵分界线的穿越，为暗能量的一般参数化推断提供理论支持。
英文摘要
Composite dynamical dark energy (DDE) has recently been explored as an efficient way to help cure cosmological tensions through the so-called $w$XCDM model (Gomez-Valent & Solà Peracaula 2024; 2025), a toy-model version of the $Λ$XCDM model (Grande et al., 2006). The latter is a composite running vacuum model (RVM) that involves a DE component $X$ (`cosmon') of generic nature. We compute the effective equation of state of $Λ$XCDM and use state-of-the-art techniques to fit this model to two standard sets of cosmological data, one involving SNIa from Pantheon$+$ and the other SNIa from DES-Dovekie, in addition to BAO data from DESI DR2 and the CMB data from Planck PR4. We do not use large scale structure formation data for this analysis nor the SH0ES calibration of $H_0$. We find that $Λ$XCDM naturally performs the crossing of the phantom divide as observed by DESI near $z\simeq 0.4$ using the $w_0w_a$CDM parameterization, a feature well favored by existing model-agnostic analyzes of the same data (González-Fuentes & Gómez-Valent:2025; 2026). It turns out that the cosmon $X$ behaves as `phantom matter' (PM) near the present, which in contrast to usual phantom DE satisfies the strong energy condition (as ordinary matter) and furnishes positive pressure ($P_X>-ρ_X>0$) at the expense of negative energy density ($ρ_X<0$). $Λ$XCDM provides a better fit than $w_0w_a$CDM and, as a bonus, alleviates the cosmic coincidence problem. Given that PM appears in stringy versions of the RVM (Mavromatos & Solà Peracaula 2021 a,b) , the $Λ$XCDM appears to be a composite DDE model with a good chance of explaining the crossing of the phantom divide from first principles, therefore providing theoretical support to the DESI observations inferred from generic parameterizations of the DE.
CommentsLaTeX, 19 pages, 2 Tables and 6 Figures, extended discussion
