We explore the predictions of ${\mathrm{\Lambda }}_{\mathrm{s}}\mathrm{CDM}$, 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 ${\mathrm{\Lambda }}_{\mathrm{s}}$ abruptly switches sign from negative to positive, attaining its present-day value at a redshift of $z_{†}\sim 2$. The ${\mathrm{\Lambda }}_{\mathrm{s}}\mathrm{CDM}$ 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 ${\mathrm{\Lambda }}_{\mathrm{s}}\mathrm{CDM}$ model on the formation and evolution of bound cosmic structures. We identify three primary influences: (i) the negative cosmological constant (AdS) phase for $z>z_{†}$, (ii) the abrupt transition marked by a type-II (sudden) singularity, leading to an abrupt increase in the Universe’s expansion rate at $z=z_{†}$, and (iii) an increased expansion rate in the late Universe under a positive cosmological constant for $z<z_{†}$, compared to $\mathrm{\Lambda }\mathrm{CDM}$. Utilizing the spherical collapse model, we investigate the nonlinear evolution of bound cosmic structures within the ${\mathrm{\Lambda }}_{\mathrm{s}}\mathrm{CDM}$ framework. We find that the virialization process of cosmic structures and, consequently, their matter overdensity vary 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-$\mathrm{\Lambda }\mathrm{CDM}$ 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.

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ΛsCDM 模型中的转变动力学：对束缚宇宙结构的影响

我们探索以下预测${\mathrm{\Lambda }}_{\mathrm{s}}\mathrm{清洁发展机制}$，一个新颖的框架表明，在宇宙晚期，在束缚的宇宙结构上，存在快速的反德西特（AdS）到德西特（dS）真空转变。最简单的版本是宇宙学常数${\mathrm{\Lambda }}_{\mathrm{s}}$突然将符号从负变为正，以红移达到当前值$z_{†}～2$。这${\mathrm{\Lambda }}_{\mathrm{s}}\mathrm{清洁发展机制}$模型成为解决主要宇宙学紧张问题的有希望的解决方案，特别是$H_0$和$S_8$紧张局势，以及其他不太明确的紧张局势。我们调查的一个关键方面是研究突发事件的影响${\mathrm{\Lambda }}_{\mathrm{s}}\mathrm{清洁发展机制}$束缚宇宙结构的形成和演化模型。我们确定了三个主要影响：（i）负宇宙常数（AdS）相位$z>z_{†}$，(ii) 以 II 型（突然）奇点为标志的突然转变，导致宇宙膨胀率在$z=z_{†}$，以及（iii）在正宇宙学常数下，晚期宇宙的膨胀率增加$z<z_{†}$， 相比$\mathrm{\Lambda }\mathrm{清洁发展机制}$。利用球形塌缩模型，我们研究了束缚宇宙结构的非线性演化${\mathrm{\Lambda }}_{\mathrm{s}}\mathrm{清洁发展机制}$框架。我们发现，宇宙结构的维氏化过程及其物质超密度的变化取决于 AdS-dS 转变是在转变之前还是之后。具体来说，与普朗克相比，结构维氏化的物质超密度增加或减少-$\mathrm{\Lambda }\mathrm{清洁发展机制}$模型，取决于转换的时间。此外，我们的结果表明，突然的奇点不会导致束缚系统的解离。尽管奇点具有深远的性质，但它对此类系统仅产生相对较弱的影响，从而增强了模型在这种情况下的可行性。