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A Lagrangian perturbation theory in the presence of massive neutrinos
Journal of Cosmology and Astroparticle Physics ( IF 6.4 ) Pub Date : 2020-10-12 , DOI: 10.1088/1475-7516/2020/10/034
Alejandro Aviles 1, 2 , Arka Banerjee 3, 4, 5
Affiliation  

We develop a Lagrangian Perturbation Theory (LPT) framework to study the clustering of cold dark matter (CDM) in cosmologies with massive neutrinos. We follow the trajectories of CDM particles with Lagrangian displacements fields up to third order in perturbation theory. Once the neutrinos become non-relativistic, their density fluctuations are modeled as being proportional to the CDM density fluctuations, with a scale-dependent proportionality factor. This yields a gravitational back-reaction that introduces additional scales to the linear growth function, which is accounted for in the higher order LPT kernels. Through non-linear mappings from Eulerian to Lagrangian frames, we ensure that our theory has a well behaved large scale behavior free of unwanted UV divergences, which are common when neutrino and CDM densities are not treated on an equal footing, and in resummation schemes that manifestly break Galilean invariance. We use our theory to construct correlation functions for both the underlying matter field, as well as for biased tracers using Convolution-LPT. Redshift-space distortions effects are modeled using the Gaussian Streaming Model. When comparing our analytical results to simulated data from the Quijote simulation suite, we find good accuracy down to $r=20 \,\text{Mpc} \, h^{-1}$ at redshift $z=0.5$, for the real space and redshift space monopole particle correlation functions with no free parameters. The same accuracy is reached for the redshift space quadrupole if we additionally consider an effective field theory parameter that shifts the pairwise velocity dispersion. For modeling the correlation functions of tracers we adopt a simple Lagrangian biasing scheme with only density and curvature operators, which we find sufficient to reach down to $r=20 \,\text{Mpc} \, h^{-1}$ when comparing to simulated halos.

中文翻译:

存在大量中微子时的拉格朗日微扰理论

我们开发了一个拉格朗日微扰理论 (LPT) 框架来研究具有大量中微子的宇宙学中冷暗物质 (CDM) 的聚类。我们在微扰理论中使用高达三阶的拉格朗日位移场来跟踪 CDM 粒子的轨迹。一旦中微子变得非相对论,它们的密度波动就被建模为与 CDM 密度波动成正比,并具有与尺度相关的比例因子。这产生了一种重力反向反应,为线性增长函数引入了额外的尺度,这在高阶 LPT 内核中得到了解释。通过从欧拉坐标系到拉格朗日坐标系的非线性映射,我们确保我们的理论具有良好的大规模行为,没有不需要的紫外线发散,当中微子和 CDM 密度没有被平等对待时,以及在明显打破伽利略不变性的恢复方案中,这是很常见的。我们使用我们的理论为基础物质场以及使用卷积 LPT 的有偏示踪剂构建相关函数。使用高斯流模型对红移空间失真效应进行建模。当将我们的分析结果与 Quijote 模拟套件的模拟数据进行比较时,我们发现在红移 $z=0.5$ 处,精确度低至 $r=20 \,\text{Mpc} \, h^{-1}$,对于没有自由参数的实空间和红移空间单极粒子相关函数。如果我们另外考虑移动成对速度色散的有效场论参数,则红移空间四极杆将达到相同的精度。
更新日期:2020-10-12
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