可变查普林金气体模型的结构增长约束
Growth-of-Structure Constraints on the Variable Chaplygin Gas Model
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中文总结 AI 辅助
本研究针对可变查普林金气体模型，结合 fσ₈ 增长测量与多类背景观测数据，发现其增长约束与背景约束存在张力，证实结构增长观测可严格检验该统一暗 sector 模型，凸显多数据结合的重要性。
中文摘要 AI 辅助
对暗物质与宇宙晚期加速膨胀的统一描述，为解释暗 sector 提供了颇具吸引力的框架。在这类模型中，可变查普林金气体（Variable Chaplygin Gas, VCG）模型虽能实现统一描述，但面临挑战，尤其是宇宙学扰动的演化问题。我们假设绝热扰动，研究 VCG 模型中线性密度扰动的演化，并在马尔可夫链蒙特卡洛（Markov Chain Monte Carlo, MCMC）框架内，利用最新的 fσ₈ 增长测量值约束其参数。高斯先验取自我们此前对背景观测的分析，包括 Ia 型超新星（Pantheon）、重子声学振荡（baryon acoustic oscillations, BAO）、哈勃参数 H(z) 测量、快速射电暴（fast radio bursts, FRB）及伽马射线暴（gamma-ray bursts, GRB）。我们发现，增长数据倾向于参数空间中与背景观测截然不同的区域，尤其增长分析偏好模型参数 n 的值显著更大（n ≈ 2.3），而背景约束下 n ≈ 1。这种张力表明，能极好拟合背景膨胀的参数值，无法同时重现观测到的宇宙结构增长。我们的结果证实，结构增长观测为统一暗 sector 模型提供了严格且独立的检验，并强调在评估可变查普林金气体模型的宇宙学可行性时，结合背景与扰动数据的重要性。
英文摘要
A unified description of dark matter and the late-time acceleration of the Universe offers an attractive framework for explaining the dark sector. Among such models, the Variable Chaplygin Gas (VCG) model provides a unified description but faces challenges, particularly in the evolution of cosmological perturbations. We investigate the evolution of linear density perturbations in the VCG model assuming adiabatic perturbations and constrain its parameters using recent $fσ_8$ growth measurements within a Markov Chain Monte Carlo (MCMC) framework. Gaussian priors are adopted from our previous analysis of background observations, including Type Ia supernovae (Pantheon), baryon acoustic oscillations (BAO), Hubble parameter $H(z)$ measurements, fast radio bursts (FRB), and gamma-ray bursts (GRB). We find that growth data favour a markedly different region of the parameter space than the background observations. In particular, the growth analysis prefers a substantially larger value of the model parameter $n$ ($n \simeq 2.3$) compared with the background constraint ($n \sim 1$). This tension indicates that parameter values providing an excellent fit to the background expansion fail to simultaneously reproduce the observed growth of cosmic structures. Our results demonstrate that growth-of-structure observations provide a stringent and independent test of unified dark sector models and underscore the importance of combining background and perturbation data when assessing the cosmological viability of the Variable Chaplygin Gas model.
发表机构
- St. Stephen’s College, University of Delhi（德里大学圣斯蒂芬斯学院）
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