AI 中文总结
该研究提出共形基灵引力（CKG）模型，利用DESI DR2等多组观测数据约束其参数，发现其倾向类精质暗能量演化，无法完全解决H0张力，为宇宙晚期加速膨胀提供新框架。
AI 中文摘要
我们研究一种称为共形基灵引力（Conformal Killing Gravity，CKG）的几何方法，在该框架中，暗能量部分自然产生于罗伯逊-沃尔克时空的共形基灵对称性。在该框架内，无散度共形基灵张量表现为一种有效理想流体，产生了一个动力学暗能量分量，其密度、压强和状态方程由基础几何唯一确定，无需引入任何经验性暗能量参数化。所得CKG模型通过一个额外参数扩展了标准ΛCDM宇宙学，同时在无几何贡献时恢复ΛCDM极限。我们使用普朗克PR4（NPIPE）的宇宙微波背景（CMB）温度、极化和引力透镜观测、ACT DR6 CMB引力透镜、DESI DR2重子声学振荡测量以及Pantheon+、DES-Dovekie和Union3 Ia型超新星汇编来约束该模型。分析表明，CKG倾向于类 quintessence（精质）的暗能量演化，无 phantom（ Phantom 态，即鬼态）穿越的证据，而重构的状态方程在宇宙早期迅速趋近于宇宙学常数。此外，该模型预测未来临界红移在-0.8 ≤ z_c ≤ -0.7范围内，表明当前宇宙膨胀在形式奇异极限z=-1之前最终会达到一个转折点。由于几何贡献仅改变复合后的膨胀历史，声视界基本保持不变，该模型无法为H0张力提供完整解决方案。我们的结果表明，CKG为描述宇宙晚期加速膨胀提供了一个简单、具有物理动机且受观测支持的框架。
英文摘要
We investigate a geometric approach referred to as the Conformal Killing Gravity (CKG), in which the dark energy sector emerges naturally from the conformal Killing symmetry of the Robertson--Walker space-time. Within this framework, the divergence-free conformal Killing tensor behaves as an effective perfect fluid, giving rise to a dynamical dark-energy component whose density, pressure, and equation of state are uniquely determined by the underlying geometry, without introducing any empirical dark-energy parametrization. The resulting CKG model extends the standard $Λ$CDM cosmology through a single additional parameter while recovering the $Λ$CDM limit in the absence of the geometric contribution. We constrain the model using Planck PR4 (NPIPE) CMB temperature, polarization, and lensing observations, ACT DR6 CMB lensing, DESI DR2 baryon acoustic oscillation measurements, and the Pantheon$+$, DES-Dovekie, and Union3 Type Ia supernova compilations. The analysis shows that the CKG favors a quintessence-like dark-energy evolution with no evidence for phantom crossing, while the reconstructed equation of state rapidly approaches the cosmological constant at earlier cosmic times. Furthermore, the model predicts a future critical redshift in the range $-0.8 \lesssim z_c \lesssim -0.7$, indicating that the present cosmic expansion eventually reaches a turning point before the formal singular limit at $z=-1$. Since the geometric contribution modifies only the post-recombination expansion history, the sound horizon remains essentially unchanged and the model does not provide a complete solution to the $H_0$ tension. Our results demonstrate that the CKG provides a simple, physically motivated, and observationally favored framework for describing the late-time accelerated expansion of the Universe.
Comments14 pages, 4 figures
Journal refPhysics of the Dark Universe 2026
DOI：10.1016/j.dark.2026.102444
