The reach of next-to-leading-order perturbation theory for the matter bispectrum
The reach of next-to-leading-order perturbation theory for the matter bispectrum
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DOI：
10.1093/mnras/stac567
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发表时间：
2021-07
影响因子：
4.8
通讯作者：
D. Alkhanishvili;C. Porciani;E. Sefusatti;M. Biagetti;A. Lazanu;Andrea Oddo;V. Yankelevich
中科院分区：
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作者：
D. Alkhanishvili;C. Porciani;E. Sefusatti;M. Biagetti;A. Lazanu;Andrea Oddo;V. Yankelevich
我们对由不同风格的微扰理论推导出来的物质双谱与来自前所未有的大型 N 体模拟套件的测量结果进行了比较。我们使用 χ2 拟合优度检验来确定模型的准确度范围，作为模拟子集覆盖的体积的函数。我们发现基于有效场理论（EFT）方法的模型具有最大的覆盖范围，标准微扰理论的覆盖范围最短，而“经典”恢复方案则介于两者之间。然而，EFT 带来的收益低于之前的研究。我们表明，EFT 预测的估计准确度范围很大程度上受到拟合反项幅度所采用的程序的影响。对于星系红移巡天探测的体积，我们的结果表明，将 EFT 双谱的三个反项设置为零并测量功率谱中的第四个是有利的。我们还发现不同实现之间的估计范围存在较大波动。我们的结论是，很难明确定义包含自由参数的模型的准确度范围。最后，我们通过尺度和形状相关偏差或通过提高测量的统计误差条（如文献中常规做法）来大致解释 N 体技术引入的系统效应。我们发现，由于可调参数的存在，后一种方法人为地扩大了 EFT 模型的范围。
We provide a comparison between the matter bispectrum derived with different flavours of perturbation theory at next-to-leading order and measurements from an unprecedentedly large suite of N-body simulations. We use the χ2 goodness-of-fit test to determine the range of accuracy of the models as a function of the volume covered by subsets of the simulations. We find that models based on the effective-field-theory (EFT) approach have the largest reach, standard perturbation theory has the shortest, and ‘classical’ resummed schemes lie in between. The gain from EFT, however, is less than in previous studies. We show that the estimated range of accuracy of the EFT predictions is heavily influenced by the procedure adopted to fit the amplitude of the counterterms. For the volumes probed by galaxy redshift surveys, our results indicate that it is advantageous to set three counterterms of the EFT bispectrum to zero and measure the fourth from the power spectrum. We also find that large fluctuations in the estimated reach occur between different realisations. We conclude that it is difficult to unequivocally define a range of accuracy for the models containing free parameters. Finally, we approximately account for systematic effects introduced by the N-body technique either in terms of a scale- and shape-dependent bias or by boosting the statistical error bars of the measurements (as routinely done in the literature). We find that the latter approach artificially inflates the reach of EFT models due to the presence of tunable parameters.