基于最新观测对单模扩散模型的约束
Constraints on unimodular diffusion models with latest observables
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中文总结 AI 辅助
研究基于违反能量 - 动量守恒产生有效宇宙学常数的情形，利用最新观测数据更新分析单模扩散模型，识别出过渡阶段，虽未显著缓解\(H_0\)张力，但为解决哈勃膨胀率差异等问题提供新思路。
中文摘要 AI 辅助
包含随时间变化状态方程的宇宙学模型最近受到探索，显示出对动态暗能量成分的偏好。本文研究一种情形，其中有效、随时间变化的宇宙学常数作为违反能量 - 动量守恒的一种涌现表现出现。此前有研究将这种能量守恒的违反作为影响物质（暗物质和重子物质）的扩散机制，在单模引力框架内导致有效暗能量成分。本文利用来自暗能量调查（DESY5）的最新Ia型超新星数据集、暗能量光谱仪（DESI）数据发布2（DR2）的重子声学振荡（BAO）测量数据，以及普朗克2018的CMB温度、极化和透镜数据进行更新分析。结果识别出一个在中间时间出现的过渡阶段，根据\(\mathrm{\Delta DIC}\)标准，相对于\(\Lambda\)CDM模型有轻微证据支持该模型。有趣的是，发现对有效宇宙学常数随时间减小或增加的演化没有决定性偏好，但稍高的\(H_0\)值更倾向于有效宇宙学常数随时间增加的情况。虽然\(H_0\)张力没有显著缓解，但这些结果表明，对扩散机制物理进行更精细建模可能为解决当前哈勃膨胀率差异提供可行途径，同时为纳入动态暗能量和解决真空能量贡献问题提供自然框架。
英文摘要
Cosmological models incorporating a time-dependent equation of state have recently been explored \cite{DESI:2025fii}, showing a preference for a dynamical dark energy component. In this work, we investigate a scenario in which an effective, time-dependent cosmological constant arises as an emergent manifestation of a violation of energy-momentum conservation. In \cite{Landau:2022mhm}, such a violation of energy conservation was studied as a diffusion mechanism affecting matter (dark and baryonic), leading to an effective dark energy component within the framework of unimodular gravity. Here, we present an updated analysis using the more recent Type Ia supernova data set from the Dark Energy Survey (DESY5) and the baryon acoustic oscillation (BAO) measurements from the Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2), along with the CMB temperature, polarization, and lensing data from Planck 2018. Our results identify a transition phase that occurs at intermediate times, with slight evidence in favor of the model relative to the $Λ$CDM according to the $\mathrm{ΔDIC}$ criterion. Interestingly, a non-decisive preference for an evolution corresponding to either a time-decreasing or time-increasing effective cosmological constant is found. However, slightly higher values of $H_0$ favor a time-increasing effective cosmological constant. Although the $H_0$ tension is not significantly alleviated, these results suggest that a more refined modeling of the physics of the diffusion mechanism may offer a viable route toward addressing the current discrepancy in the Hubble expansion rate, while also providing a natural framework for incorporating a dynamical dark energy and addressing the problem of vacuum energy contribution.
