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arXiv 2404.02783astro-ph.CO
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从宇宙学视界到暗晕尺度的宇宙模拟

Simulating the Universe from the cosmological horizon to halo scales

Thomas Montandon, Oliver Hahn, Clément Stahl

AI总结:

针对超大规模宇宙模拟的动力学范围限制问题,本研究结合gevolution相对论代码与Gadget-4牛顿模拟实现有效模拟,首次测得泊松规范下的相对论尺度依赖偏置值,为相关宇宙学观测分析提供支撑。

摘要:

即将开展的观测项目将探测接近宇宙学视界的超大规模尺度。这些尺度有望对单场暴胀以及广义相对论进行约束,但要将其纳入后续分析,其建模必须具备稳健性。尤其是广义相对论效应可能被误认为是原初信号,而无论是解析建模还是数值模拟路径都尚未达成共识,这一困境受限于所需模拟的巨大动力学范围。在本研究中,我们提出了一种数值技术以克服上述限制:我们使用N体相对论代码gevolution(一种相对论宇宙学N体模拟程序)计算广义相对论位移场,并将其与精确的牛顿模拟程序Gadget-4相结合。这种组合得到的有效模拟能够在物质功率谱和双谱层面复现预期的行为。随后我们首次在模拟中测量了泊松规范下的相对论性尺度依赖偏置;在红移$z=0$时,我们得到$b_1^{\text{GR}}=-5.7 \pm 1.7$。我们在场层面的结果仅在泊松规范下成立,还需要结合相对论性光线追踪算法来计算可观测的星系数密度。

英文摘要:

Ultra-large scales close to the cosmological horizon will be probed by the upcoming observational campaigns. They hold the promise to constrain single-field inflation as well as general relativity, but in order to include them in the forthcoming analyses, their modelling has to be robust. In particular, general relativistic effects may be mistaken for primordial signals, and no consensus has emerged either from analytical modelling nor from the numerical route, obstructed by the large dynamical range to be simulated. In this work, we present a numerical technique to overcome the latter limitation: we compute the general relativistic displacement field with the N-body relativistic code gevolution and combine it with the accurate Newtonian simulation Gadget-4. This combination leads to an effective simulation reproducing the desired behaviour at the level of the matter power spectrum and bispectrum. We then measure, for the first time in a simulation, the relativistic scale-dependent bias in Poisson gauge; at redshift $z=0$, we find $b_1^{\mathrm{GR}}=-5.7 \pm 1.7$. Our results at the field level are only valid in the Poisson gauge and need to be complemented with a relativistic ray tracing algorithm to compute the number count observable.

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