发表机构
Universitat de Barcelona (UB)（巴塞罗那大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文研究非最小耦合标量场模型，在无屏蔽机制下通过正耦合参数实现幻影分割穿越，满足局部约束，并首次进行蒙特卡洛分析，显示对暗能量模型的适度偏好。
AI 中文摘要
近期关于动态暗能量的迹象，包括可能穿越幻影分割线，促使人们寻找可行的理论解释。具有形式为 $F(\varphi)=1+\alpha\varphi^2$ 的耦合的非最小耦合到引力的标量场已成为有希望的候选者，与 $\Lambda$CDM 甚至 $w_0w_a$CDM 参数化相比，它们提供了对数据的改进拟合。然而，在缺乏屏蔽机制的情况下，迄今为止详尽研究的参数空间区域（$\alpha<0$）违反了关于引力强度和时变性的严格局部约束，并增强了低红移处的物质增长速率，从而损害了这些解的可行性。在这项工作中，我们研究了一个很大程度上未被探索的参数空间区域（$\alpha>0$），该区域实现了穿越，同时与局部约束保持一致。这种设置虽然需要一些微调，但遵守了 BBN 约束，并且仅导致有效引力耦合与牛顿常数的偏差在过去低于 $0.3\\%$。我们回顾了该模型的背景和线性扰动动力学，推导出提供对其行为物理洞察的解析结果，并使用最新的宇宙学数据（包括 DES-Dovekie 超新星样本）更新了模型的约束。我们首次对 $\alpha>0$ 进行了完整的蒙特卡洛分析，研究了 $G$ 的变化对超新星绝对光度的影响，并将结果与 $\alpha<0$ 的情况进行了比较，两种情况均使用线性势。在具有非最小耦合且 $\alpha<0$ 的模型背景下，标准模型在 $2.50\sigma$ 置信水平被排除，而对于 $\alpha>0$，排除显著性降至约 $2\sigma$ 置信水平，表明这些模型相对于 $\Lambda$CDM 有适度的偏好。[删节]
英文摘要
Recent hints of dynamical dark energy, including a possible crossing of the phantom divide, have motivated the search for viable theoretical explanations. Scalar fields non-minimally coupled to gravity with a coupling of the form $F(φ)=1+αφ^2$ have emerged as promising candidates, providing an improved fit to the data compared to $Λ$CDM and even the $w_0w_a$CDM parametrization. However, in the absence of a screening mechanism, the regions of parameter space examined exhaustively so far (with $α<0$) violate stringent local constraints on the strength and time variation of gravity and enhance the matter growth rate at low redshifts, thereby compromising the viability of these solutions. In this work, we investigate a largely unexplored region of parameter space (with $α>0$) that realizes the crossing while remaining consistent with local constraints. This setup, which is subject to some fine-tuning, respects the BBN constraints and leads only to deviations of the effective gravitational coupling from Newton's constant below $0.3%$ in the past. We review the background and linear perturbation dynamics of the model, deriving analytical results that provide physical insight into its behavior, and update the constraints on the model using the latest cosmological data, including the DES-Dovekie supernova sample. We perform for the first time a full-fledged Monte Carlo analysis with $α>0$, studying the impact of the variation of $G$ on the supernovae absolute luminosity, and compare the results with those obtained for $α<0$, using in both cases a linear potential. In the context of the model with non-minimal coupling and $α<0$, the standard model is excluded at the $2.50σ$ CL, whereas for $α>0$, the exclusion significance decreases to $\sim 2σ$ CL, indicating a moderate preference for these models over $Λ$CDM. [abridged]
Comments51 pages, 13 figures, 1 table
