两种耦合的故事：相互作用暗 sector 中的贝叶斯选择
A Tale of Two Couplings: Bayesian Selection in the Interacting Dark Sector
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中文总结 AI 辅助
针对 ΛCDM 的 σ₈ 张力，研究第五元素与暗物质的共形和非共形耦合暗 sector 模型，发现纯共形耦合模型统计偏好更强，优于 ΛCDM 基线。
中文摘要 AI 辅助
ΛCDM 为宇宙提供了极为成功的描述，但仍存在持续的偏差，其中最突出的是早期宇宙宇宙微波背景（CMB）测量与晚期结构增长探测之间的 σ₈ 张力。为解决这一不匹配问题，我们研究由第五元素（quintessence）场通过共形和非共形变换与暗物质耦合的广义相互作用暗 sector 模型。通过通用设计第五元素势，确保暗物质与暗能量的联合演化完全模仿 ΛCDM，我们的模型满足所有背景约束，同时在线性微扰领域显示出修正引力效应。我们使用锚定到普朗克 2018 约束的晚期结构增长数据进行统计分析。此外，我们解决了纯非共形模型固有的初始条件问题，证明需要非零初始动能来启动动力学演化。我们的结果表明，纯共形耦合能有效地将能量从暗物质转移到第五元素场，抑制晚期结构形成，并成功将 CMB 数据纳入晚期修正结构增长中。根据赤池信息准则和贝叶斯信息准则，这种纯共形极限比 ΛCDM 基线具有更强的统计偏好。相反，虽然非零非共形耦合引入了动能摩擦，抑制了暗 sector 的能量交换，但它们扩展的参数空间带来了沉重的统计惩罚，未比纯共形场景提供决定性改进。
英文摘要
$Λ$CDM provides a remarkably successful description of the Universe, yet it suffers from persistent discrepancies, with one of the most prominent being the $σ_8$ tension between early-Universe Cosmic Microwave Background (CMB) measurements and late-time structure growth probes. To address this mismatch, we investigate generalized interacting dark sector models governed by a quintessence field coupled to dark matter via conformal and disformal transformations. By generically engineering a quintessence potential that ensures the combined evolution of dark matter and dark energy exactly mimics $Λ$CDM, our models satisfy all background constraints while signaling modified gravity effects within the linear perturbation sector. We perform a statistical analysis using late-time structure growth data anchored to Planck 2018 constraints. Furthermore, we address the initial conditions problem inherent to purely disformal models, demonstrating the necessity of a non-zero initial kinetic energy to initiate dynamical evolution. Our results indicate that purely conformal couplings efficiently transfer energy from dark matter to the quintessence field, suppressing late-time structure formation and successfully accommodating CMB data within late-time modified structure growth. This purely conformal limit yields a strong statistical preference over the $Λ$CDM baseline according to both the Akaike and Bayesian Information Criteria. Conversely, while non-zero disformal couplings introduce a kinetic friction that dampens the dark sector energy exchange, their expanded parameter space incurs heavy statistical penalties without providing a decisive improvement over the purely conformal scenario.
