发表机构
University of Trento; Trento Institute for Fundamental Physics and Applications (TIFPA)-INFN; University of Hawai‘i; Shanghai Jiao Tong University; University of Sheffield（特伦托大学; 特伦托基础物理与应用研究所（TIFPA）-意大利国家核物理研究所; 夏威夷大学; 上海交通大学; 谢菲尔德大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究测试了压缩CMB似然函数在约束ΛCDM之外新物理时的可靠性，发现其对晚期暗能量扩展仍准确，但修改暗物质演化会破坏映射关系导致约束严重失效。
AI 中文摘要
我们测试了压缩后的CMB似然函数在何种情况下能够可靠地用于约束ΛCDM之外的新物理，并针对CMB压缩失效的“何时”、“为何”以及“如何”制定了具体标准。我们通过探索一系列修改宇宙演化不同方面的模型来得出我们的结论，这些模型包括晚期暗能量动力学、通过相互作用或衰变产生的非标准晚期暗物质演化，以及具有持续非标准红移演化的暗物质模型。对于每种情况，我们将基于完整Planck-CMB似然函数的数据组合所得结果，与基于在ΛCDM中校准的压缩CMB似然函数所得结果进行比较。我们发现，对于保留暗物质背景演化且不引入显著额外微扰效应的晚期暗能量扩展模型，压缩仍然准确。相比之下，修改暗物质演化会破坏当前物质密度与CMB相关时期物质密度之间的映射关系，即使这种修改仅发生在晚期，也会导致压缩约束失效。在这些情况下，压缩似然函数会极大地改变多维后验分布的几何形状，移动其中心，产生强各向异性形变，重新排列主模式，并导致其特征方向发生真正的混合和旋转。这些多维畸变会传播到对宇宙学参数严重错误的边际约束中，在本研究涉及的某些案例中，完整分析与压缩分析之间的差异接近一个数量级。
英文摘要
We test when compressed CMB likelihoods can be reliably used to constrain new physics beyond $Λ$CDM, formulating concrete criteria for \textit{when}, \textit{why}, and \textit{how} CMB compression fails. We derive our conclusions by exploring a broad set of models that modify different aspects of the cosmological evolution, including late-time dark-energy dynamics, non-standard late-time dark-matter evolution through interactions or decay, and dark-matter models with persistently non-standard redshift evolution. For each case, we compare the results obtained from data combinations based on the full Planck-CMB likelihood with their counterparts based on a compressed CMB likelihood calibrated in $Λ$CDM. We find that the compression remains accurate for late-time dark-energy extensions that preserve the dark-matter background evolution and do not introduce significant additional perturbative effects. By contrast, modifying the dark-matter evolution breaks the mapping between the present-day matter density and the matter density at the epochs relevant to the CMB, causing the compressed constraints to fail even when the modification acts exclusively at late times. In these cases, the compressed likelihood can drastically alter the geometry of the multidimensional posterior distributions, shifting their centers, producing strongly anisotropic deformations, reordering principal modes, and generating genuine mixing and rotation of their eigendirections. These multidimensional distortions propagate into substantially incorrect marginalized constraints on cosmological parameters, with differences between the full and compressed analyses reaching nearly an order of magnitude in some of the cases studied here.
Comments21 pages, 10 figures. 1 appendix with 3 figures
