标题： $Λ_{\rm s}$类型II极小修正引力的CDM宇宙学 显示英文标题

标题： $Λ_{\rm s}$CDM cosmology from a type-II minimally modified gravity

摘要： 我们成功地将一个有前景的缓解宇宙张力的模型$\Lambda_{\rm s}$CDM 整合进了一个理论框架，并通过赋予它来自类型II极小修正引力的 VCDM 模型的一个特定拉格朗日，使其具备了相应的理论基础。在这个理论中，我们证明了一个具有线性势的辅助标量场能够诱导出一个有效的宇宙学常数，从而通过分段线性势实现在晚期宇宙中的突然镜像AdS-dS转变。为了消除该设定下的突变奇点并确保稳定的转变，我们对该势能进行了平滑处理。 在 VCDM 理论框架下实现的$\Lambda_{\rm s}$CDM 模型促进了两种类型的快速平滑镜像AdS-dS转变：(i) 激动型转变，与势能的平滑跳跃相关联，在这种情况下，$\Lambda_{\rm s}$和随后的$H$在转变的中点附近表现出一个凸起；(ii) 宁静型转变，与势能斜率的平滑变化相关联，在这种情况下，$\Lambda_{\rm s}$转变得非常平稳。这些转变可能在背景和扰动动力学上留下不同的印记，这可能使观测数据能够区分它们。 这一新颖的理论框架推动了$\Lambda_{\rm s}$CDM 成为一种完全可预测的模型，能够探索包括晚期AdS-dS转变时期在内的宇宙演化过程，并扩展了模型的应用范围。我们相信进一步的研究对于确立$\Lambda_{\rm s}$CDM 作为新的和谐宇宙学模型的主要候选者或指导者至关重要。 显示英文摘要

摘要： We have successfully integrated $\Lambda_{\rm s}$CDM, a promising model for alleviating cosmological tensions, into a theoretical framework by endowing it with a specific Lagrangian from the VCDM model, a type-II minimally modified gravity. In this theory, we demonstrate that an auxiliary scalar field with a linear potential induces an effective cosmological constant, enabling the realization of an abrupt mirror AdS-dS transition in the late universe through a piecewise linear potential. To eliminate the sudden singularity in this setup and ensure stable transitions, we smooth out this potential. Realized within the VCDM theory, the $\Lambda_{\rm s}$CDM model facilitates two types of rapid smooth mirror AdS-dS transitions: (i) the agitated transition, associated with a smooth jump in the potential, where $\Lambda_{\rm s}$, and consequently $H$, exhibits a bump around the transition's midpoint; and (ii) the quiescent transition, associated with a smooth change in the slope of the potential, where $\Lambda_{\rm s}$ transitions gracefully. These transitions are likely to leave distinct imprints on the background and perturbation dynamics, potentially allowing the observational data to distinguish between them. This novel theoretical framework propels $\Lambda_{\rm s}$CDM into a fully predictive model capable of exploring the evolution of the Universe including the late-time AdS-dS transition epoch, and extends the applicability of the model. We believe further research is crucial in establishing $\Lambda_{\rm s}$CDM as a leading candidate or guide for a new concordance cosmological model.