用观测数据发现宇宙膨胀率在特定红移处存在显著异常，可能指向新物理。
New Expansion Rate Anomalies at Characteristic Redshifts Geometrically Determined using DESI-DR2 BAO and DES-SN5YR Observations
- 基于双数据集与两种方法重建宇宙距离，确定7个特征红移点。
- 在z≈0.35-0.55区间，膨胀率偏离标准模型达4至5σ。
- 结果稳健且独立于方法，提示晚期宇宙演化或有未知物理机制。
我们采用多任务高斯过程（MTGP）与基于节点的样条技术，结合DESI-DR2 BAO与DES-SN5YR数据，对宇宙距离进行模型无关重建，并将声子拖曳时期共动声速尺度 $r_d$ 校准至普朗克值以保证早期宇宙物理一致性。利用重构的距离及其导数，我们获得 $0.3 \leq z \leq 1.7$ 范围内的七个特征红移点，计算出这些红移下的归一化膨胀率 $E(z)$。结果揭示其与普朗克2018 $Λ$CDM预测相比存在约4至5σ的显著偏差，尤其在 $z \sim 0.35-0.55$ 区间尤为突出。该异常在两种重建方法及联合数据下均一致出现，表明晚期宇宙膨胀率存在稳健张力，且不同于已知的“哈勃张力”。这可能暗示标准宇宙框架之外的新物理存在于该红移区间。研究强调特征红移作为膨胀率异常敏感指标的作用，并呼吁未来利用DESI-5YR BAO、欧几里得（Euclid）和大型巡天望远镜（LSST）数据进一步验证，以区分是新物理还是数据系统误差所致。
原文摘要 · Abstract (English)
We perform a model-independent reconstruction of the cosmic distances using the Multi-Task Gaussian Process (MTGP) framework as well as knot-based spline techniques with DESI-DR2 BAO and DES-SN5YR datasets. We calibrate the comoving sound horizon at the baryon drag epoch $r_d$ to the Planck value, ensuring consistency with early-universe physics. With the reconstructed cosmic distances and their derivatives, we obtain seven characteristic redshifts in the range $0.3 \leq z \leq 1.7$. We derive the normalized expansion rate of the Universe $E(z)$ at these redshifts. Our findings reveal significant deviations of approximately $4$ to $5σ$ from the Planck 2018 $Λ$CDM predictions, particularly pronounced in the redshift range $z \sim 0.35-0.55$. These anomalies are consistently observed across both reconstruction methods and combined datasets, indicating robust late-time tensions in the expansion rate of the Universe and which are distinct from the existing "Hubble Tension". This could signal new physics beyond the standard cosmological framework at this redshift range. Our findings underscore the role of characteristic redshifts as sensitive indicators of expansion rate anomalies and motivate further scrutiny with forthcoming datasets from DESI-5YR BAO, Euclid, and LSST. These future surveys will tighten constraints and will confirm whether these late-time anomalies arise from new fundamental physics or unresolved systematics in the data.
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