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| Format: | Preprint |
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2026
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| Online Access: | https://arxiv.org/abs/2603.27673 |
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| _version_ | 1866910087241531392 |
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| author | Zhang, Yupeng Tian, Shuxun Li, Zhengxiang |
| author_facet | Zhang, Yupeng Tian, Shuxun Li, Zhengxiang |
| contents | We study whether an open FLRW Universe with a negative cosmological constant can evade the eventual recollapse characteristic of AdS-type Universe. Within a power-law realization of Fab-Four theory, we solve the background equations numerically and analyze the asymptotic dynamics. We find that the scalar sector provides a self-tuning-like compensation of the negative Λ while leaving the spatial-curvature term unscreened. Consequently, the expansion does not reverse. Instead, the Universe evolves toward a curvature-dominated linear-expansion regime, a {\propto} t. To probe the underlying compensation mechanism, we further analyze an auxiliary zero-curvature subsystem using Poincaré compactification. The physically admissible trajectories approach a critical point at infinity where the compensating scalar-Λ sector becomes stiff-like (w_{ϕ+Λ} {\to} 1), so that its effective energy density redshifts faster than curvature (w_k = -1/3). Although this auxiliary analysis does not cover the full curved cosmology, it is consistent with and qualitatively supports the numerical finding that the net ϕ + Λ contribution becomes subdominant to curvature, thereby preventing recollapse despite Λ < 0. This extends the application of the self-tuning mechanism to the AdS region and offers a possibility for the AdS Universe predicted by string theory to become a reality. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_27673 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Avoiding recollapse in an open-AdS Universe via a self-tuning-like mechanism Zhang, Yupeng Tian, Shuxun Li, Zhengxiang Cosmology and Nongalactic Astrophysics We study whether an open FLRW Universe with a negative cosmological constant can evade the eventual recollapse characteristic of AdS-type Universe. Within a power-law realization of Fab-Four theory, we solve the background equations numerically and analyze the asymptotic dynamics. We find that the scalar sector provides a self-tuning-like compensation of the negative Λ while leaving the spatial-curvature term unscreened. Consequently, the expansion does not reverse. Instead, the Universe evolves toward a curvature-dominated linear-expansion regime, a {\propto} t. To probe the underlying compensation mechanism, we further analyze an auxiliary zero-curvature subsystem using Poincaré compactification. The physically admissible trajectories approach a critical point at infinity where the compensating scalar-Λ sector becomes stiff-like (w_{ϕ+Λ} {\to} 1), so that its effective energy density redshifts faster than curvature (w_k = -1/3). Although this auxiliary analysis does not cover the full curved cosmology, it is consistent with and qualitatively supports the numerical finding that the net ϕ + Λ contribution becomes subdominant to curvature, thereby preventing recollapse despite Λ < 0. This extends the application of the self-tuning mechanism to the AdS region and offers a possibility for the AdS Universe predicted by string theory to become a reality. |
| title | Avoiding recollapse in an open-AdS Universe via a self-tuning-like mechanism |
| topic | Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2603.27673 |