标题： Transition dynamics in the $Λ_{\rm s}$CDM model: Implications for bound cosmic structures 显示英文标题

标题： Transition dynamics in the $Λ_{\rm s}$CDM model: Implications for bound cosmic structures

摘要： 我们研究了$\Lambda_{\rm s}$CDM 模型的预测，这是一种新框架，表明宇宙晚期存在从反德西特（AdS）到德西特（dS）真空的快速转变，适用于束缚宇宙结构。 在最简单的版本中，宇宙学常数$\Lambda_{\rm s}$突然从负值变为正值，在红移为${z_\dagger\sim 2}$时达到其当前值。 $\Lambda_{\rm s}$CDM 模型成为解决主要宇宙学张力的一个有前景的方案，特别是$H_0$和$S_8$张力，以及其他一些不太明确的张力。 我们研究的一个关键方面是考察突然的$\Lambda_{\rm s}$CDM 模型对束缚宇宙结构形成和演化的影响。 我们识别出三个主要影响因素：(i) 对于$z > z_\dagger$的负宇宙学常数（AdS）相；(ii) 标记为 II 型（突然）奇点的急剧转变，在$z=z_\dagger$导致宇宙膨胀率突然增加；(iii) 在正宇宙学常数下，对于$z < z_\dagger$晚期宇宙的膨胀率增加，与$\Lambda$冷暗物质（CDM）相比。 利用球形坍缩模型，我们在$\Lambda_{\rm s}$冷暗物质（CDM）框架内研究了束缚宇宙结构的非线性演化。 我们发现，宇宙结构的暴胀化过程以及随之而来的物质过密性变化取决于 AdS-dS 转变发生在回转之前还是之后。 具体来说，结构的暴胀化伴随着比普朗克-$\Lambda$冷暗物质（CDM）模型增加或减少的物质过密性，这取决于转变的时间。 此外，我们的结果显示，突然奇点不会导致束缚系统的解体。 尽管它的深远影响，这个奇点对这些系统施加的影响相对较小，从而增强了该模型在这个背景下的可行性。 显示英文摘要

摘要： We explore the predictions of $\Lambda_{\rm s}$CDM, a novel framework suggesting a rapid anti-de Sitter (AdS) to de Sitter (dS) vacua transition in the late Universe, on bound cosmic structures. In its simplest version, the cosmological constant, $\Lambda_{\rm s}$, abruptly switches sign from negative to positive, attaining its present-day value at a redshift of ${z_\dagger\sim 2}$. The $\Lambda_{\rm s}$CDM model emerges as a promising solution to major cosmological tensions, particularly the $H_0$ and $S_8$ tensions, as well as other less definite tensions. A key aspect of our investigation is examining the impact of the abrupt $\Lambda_{\rm s}$CDM model on the formation and evolution of bound cosmic structures. We identify three primary influences: (i) the negative cosmological constant (AdS) phase for $z > z_\dagger$, (ii) the abrupt transition marked by a type II (sudden) singularity, leading to an abrupt increase in the universe's expansion rate at $z=z_\dagger$, and (iii) an increased expansion rate in the late universe under a positive cosmological constant for $z < z_\dagger$, compared to $\Lambda$CDM. Utilizing the spherical collapse model, we investigate the non-linear evolution of bound cosmic structures within the $\Lambda_{\rm s}$CDM framework. We find that the virialization process of cosmic structures, and consequently their matter overdensity, varies depending on whether the AdS-dS transition precedes or follows the turnaround. Specifically, structures virialize with either increased or reduced matter overdensity compared to the Planck-$\Lambda$CDM model, contingent on the timing of the transition. Additionally, our results demonstrate that the sudden singularity does not result in the dissociation of bound systems. Despite its profound nature, the singularity exerts only relatively weak effects on such systems, thereby reinforcing the model's viability in this context.