Nonlinear Matter Power Spectrum from relativistic $N$-body Simulations: $Λ_{\rm s}$CDM versus $Λ$CDM
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| Format: | Preprint |
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2025
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| author | Akarsu, Özgür Di Valentino, Eleonora Vyskočil, Jiří Yılmaz, Ezgi Yükselci, A. Emrah Zhuk, Alexander |
| author_facet | Akarsu, Özgür Di Valentino, Eleonora Vyskočil, Jiří Yılmaz, Ezgi Yükselci, A. Emrah Zhuk, Alexander |
| contents | We present relativistic $N$-body simulations of a $Λ_{\rm s}$CDM - sign-switching cosmological constant (CC) - scenario under general relativity and compare its nonlinear matter power spectrum to $Λ$CDM at ${z = 15,\,2,\,1,\,0}$, using best-fit parameters from Planck-only and a combined ''full'' dataset. During the AdS-like CC ($Λ_{\rm s}<0$) phase, prior to the transition redshift $z_\dagger$, reduced Hubble friction dynamically enhances the growth of perturbations; after the switch, with dS-like CC ($Λ_{\rm s}>0$), the larger late-time expansion rate partly suppresses, but does not erase, the earlier amplification. Consequently, the ratio $P_{Λ_{\rm s}\rm CDM}/P_{Λ\rm CDM}$ exhibits a pronounced, redshift-dependent shape feature: a crest peaking at ${\sim 20-25\%}$ around ${k \simeq 1-3\,h\,\mathrm{Mpc}^{-1}}$ near the transition, which then migrates to larger physical scales and persists to ${z = 0}$ as a robust ${\sim 15-20\%}$ uplift at ${k \simeq 0.6-1.0\,h\,\mathrm{Mpc}^{-1}}$. These wavenumbers correspond to group or poor-cluster environments and lie within the sensitivity range of weak lensing, galaxy-galaxy lensing, cluster counts, and tSZ power, providing a concrete, falsifiable target that cannot be mimicked by a scale-independent change in $σ_8$ or $S_8$. The timing (earlier for Planck-only, later for the full dataset) and the amplitude of the crest align with the ''cosmic noon'' epoch (${z \simeq 1-2}$), offering a gravitational prior for the observed peak in the cosmic star-formation rate. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2510_18741 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Nonlinear Matter Power Spectrum from relativistic $N$-body Simulations: $Λ_{\rm s}$CDM versus $Λ$CDM Akarsu, Özgür Di Valentino, Eleonora Vyskočil, Jiří Yılmaz, Ezgi Yükselci, A. Emrah Zhuk, Alexander Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology We present relativistic $N$-body simulations of a $Λ_{\rm s}$CDM - sign-switching cosmological constant (CC) - scenario under general relativity and compare its nonlinear matter power spectrum to $Λ$CDM at ${z = 15,\,2,\,1,\,0}$, using best-fit parameters from Planck-only and a combined ''full'' dataset. During the AdS-like CC ($Λ_{\rm s}<0$) phase, prior to the transition redshift $z_\dagger$, reduced Hubble friction dynamically enhances the growth of perturbations; after the switch, with dS-like CC ($Λ_{\rm s}>0$), the larger late-time expansion rate partly suppresses, but does not erase, the earlier amplification. Consequently, the ratio $P_{Λ_{\rm s}\rm CDM}/P_{Λ\rm CDM}$ exhibits a pronounced, redshift-dependent shape feature: a crest peaking at ${\sim 20-25\%}$ around ${k \simeq 1-3\,h\,\mathrm{Mpc}^{-1}}$ near the transition, which then migrates to larger physical scales and persists to ${z = 0}$ as a robust ${\sim 15-20\%}$ uplift at ${k \simeq 0.6-1.0\,h\,\mathrm{Mpc}^{-1}}$. These wavenumbers correspond to group or poor-cluster environments and lie within the sensitivity range of weak lensing, galaxy-galaxy lensing, cluster counts, and tSZ power, providing a concrete, falsifiable target that cannot be mimicked by a scale-independent change in $σ_8$ or $S_8$. The timing (earlier for Planck-only, later for the full dataset) and the amplitude of the crest align with the ''cosmic noon'' epoch (${z \simeq 1-2}$), offering a gravitational prior for the observed peak in the cosmic star-formation rate. |
| title | Nonlinear Matter Power Spectrum from relativistic $N$-body Simulations: $Λ_{\rm s}$CDM versus $Λ$CDM |
| topic | Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2510.18741 |