宇宙重子流体的非高斯性：对数泊松层次模型
Non-Gaussianity of the Cosmic Baryon Fluid: Log-Poisson Hierarchy Model
摘要：
在非线性的宇宙成团机制中，宇宙重子流体的质量密度场是高度非高斯的。它表现出与无碰撞暗物质不同的动力学行为。然而，在从Jeans长度到几十个h^{-1} Mpc的范围内，重子流体的演化场是标度协变的，其中动力学方程和初始微扰是无标度的。在无标度范围内，膨胀宇宙中由纳维-斯托克斯方程控制的宇宙重子流体的非高斯特性可以用log-Poisson分级级联来描述.对数泊松格式是一个随机乘性过程，即使在高斯场的情况下，也会导致非高斯性和非线性。log-Poisson RMP包含两个无量纲参数：$β$表示非线性，$γ$表示最奇异的结构。log-Poisson RMP模型给出的所有预测，包括层次关系、间歇指数的阶数依赖、矩和尺度-尺度相关，都与标准冷暗物质模型的流体动力学模拟结果符合得很好.间歇参数$β$在低红移处略有减小，表明重子流体密度场在低红移处包含更多的奇异结构。该模型的适用性。
英文摘要：
In the nonlinear regime of cosmic clustering, the mass density field of the cosmic baryon fluid is highly non-Gaussian. It shows different dynamical behavior from collisionless dark matter. Nevertheless, the evolved field of baryon fluid is scale-covariant in the range from the Jeans length to a few ten h^{-1} Mpc, in which the dynamical equations and initial perturbations are scale free. We show that in the scale-free range, the non-Gaussian features of the cosmic baryon fluid, governed by the Navier-Stokes equation in an expanding universe, can be well described by a log-Poisson hierarchical cascade. The log-Poisson scheme is a random multiplicative process (RMP), which causes non-Gaussianity and intermittency even when the original field is Gaussian. The log-Poisson RMP contains two dimensionless parameters: $β$ for the intermittency and $γ$ for the most singular structure. All the predictions given by the log-Poisson RMP model, including the hierarchical relation, the order dependence of the intermittent exponent, the moments, and the scale-scale correlation, are in good agreement with the results given by hydrodynamic simulations of the standard cold dark matter model. The intermittent parameter $β$ decreases slightly at low redshift and indicates that the density field of baryon fluid contains more singular structures at lower redshifts. The applicability of the model is addressed.
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