从最新宇宙学数据重建标量场动力学的高斯过程方法
Gaussian process reconstruction of scalar field dynamics from recent cosmological data
浏览论文内容
中文总结 AI 辅助
该研究采用高斯过程回归，结合多组宇宙学数据重建暗能量标量场动力学，发现晚期势接近ΛCDM模型，z~0.5附近有phantom分界穿越的轻微迹象，空间曲率影响极小。
中文摘要 AI 辅助
我们利用现有宇宙学数据重建晚期宇宙膨胀历史与暗能量动力学，将暗能量视为有效且最小耦合的正则标量场，不假设其势的具体形式。重建采用高斯过程（GP）回归，联合数据集包含32个宇宙计时仪测量值（CC32）、DESI DR2重子声学振荡数据、3个Ia型超新星汇编（Pantheon+、Union3与DES Y5），以及压缩的CMB距离先验。从重建的哈勃参数及其导数，我们得到标量场的动能与势能密度、状态方程w(z)，以及标量场势的无量纲斜率参数|λ(z)|。重建的势在晚期几乎恒定，为Ṽ(0)≃0.68–0.70ρ_c,0，与平坦ΛCDM模型中的暗能量密度接近。在0≲z≲2.5范围内，动能项保持较小，而w(z)在不确定度范围内始终接近-1。仅使用CC32与DESI DR2数据时，我们发现z~0.5附近存在 phantom 分界穿越的轻微（1σ）迹象，但该特征依赖于超新星汇编，无法作为当前数据下的确定结论。斜率参数|λ(z)|呈现轻微演化，当前中心值约为0.8–1.0，但因依赖膨胀历史的高阶导数而存在较大不确定度。曲率参数Γ(z)需要更高阶导数，当前数据无法约束，故不报告其重建结果。允许空间曲率Ω_k=0–0.02，仅使结果发生微小变化，且仍在现有不确定度带内。
英文摘要
We reconstruct the late-time expansion history and dark energy dynamics using available cosmological data. We consider dark energy as an effective minimally coupled canonical scalar field without assuming a specific form for its potential. For reconstruction, we use Gaussian Process (GP) regression with a joint dataset consisting of 32 cosmic chronometer measurements (CC32), DESI DR2 baryon acoustic oscillation data, three Type Ia supernova compilations (Pantheon+, Union3, and DES Y5), and compressed CMB distance priors. From the reconstructed Hubble parameter and its derivatives, we obtain the scalar field kinetic and potential energy densities, the equation of state $w(z)$, and the dimensionless slope parameter $|λ(z)|$ of the scalar field potential. The reconstructed potential is nearly constant at late times, with $\tilde{V}(0) \simeq 0.68$--$0.70ρ_{c,0}$, close to the dark-energy density in flat $Λ$CDM. The kinetic term remains small over $0 \lesssim z \lesssim 2.5$, while $w(z)$ remains close to $-1$ within the uncertainties. Using only CC32 and DESI DR2, we find a mild ($1σ$) hint of a phantom-divide crossing near $z\sim0.5$. However, this feature depends on the supernova compilation and cannot be regarded as a firm conclusion with current data. The slope parameter $|λ(z)|$ shows mild evolution, with present-day central values around $0.8$--$1.0$, but large uncertainties due to its dependence on higher-order derivatives of the expansion history. The curvature parameter $Γ(z)$ requires even higher-order derivatives and is not constrained by current data; therefore, we do not report its reconstruction. Allowing small spatial curvature, $Ω_k=0$--$0.02$, changes the results only slightly and remains within the existing uncertainty bands.
