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arXiv 1208.0839astro-ph.COgr-qchep-phhep-th
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暗物质的有效场论与结构形成:半解析结果

The Effective Field Theory of Dark Matter and Structure Formation: Semi-Analytical Results

Mark P. Hertzberg

摘要:

补充最近的工作的有效场论的宇宙大尺度结构,在这里,我们提出了详细的近似分析结果和进一步的教学理解的方法。我们从无碰撞玻尔兹曼方程出发,积分出暗物质/暗能量主导宇宙(LambdaCDM)的短模,其物质是由大质量粒子组成的。这建立了一个长距离的有效流体,有效的长度尺度大于非线性尺度~ 10 Mpc,并提供了完整的描述大尺度结构的形成。提取的时间依赖性,我们推导出递归关系,编码的微扰解。这对于物质主导的时代是准确的,在Lambda CDM中也是相当准确的。有效流体的特征在于物理参数,包括声速和粘度。这两个流体参数相互之间起着简并的作用,并导致标准微扰理论的相对修正,其形式为~ 10^{-6 $> c^2k^2/H^2。从线性理论出发,我们计算宇宙学观测量的修正,如重子声振荡峰,我们计算半解析单圈阶。由于非零的流体参数,有效场论的预测同意观察更准确地比标准微扰理论,我们解释了为什么。我们还讨论了将暗物质视为相互作用或波动等问题的修正。

英文摘要:

Complimenting recent work on the effective field theory of cosmological large scale structures, here we present detailed approximate analytical results and further pedagogical understanding of the method. We start from the collisionless Boltzmann equation and integrate out short modes of a dark matter/dark energy dominated universe (LambdaCDM) whose matter is comprised of massive particles as used in cosmological simulations. This establishes a long distance effective fluid, valid for length scales larger than the non-linear scale ~ 10 Mpc, and provides the complete description of large scale structure formation. Extracting the time dependence, we derive recursion relations that encode the perturbative solution. This is exact for the matter dominated era and quite accurate in LambdaCDM also. The effective fluid is characterized by physical parameters, including sound speed and viscosity. These two fluid parameters play a degenerate role with each other and lead to a relative correction from standard perturbation theory of the form ~ 10^{-6}c^2k^2/H^2. Starting from the linear theory, we calculate corrections to cosmological observables, such as the baryon-acoustic-oscillation peak, which we compute semi-analytically at one-loop order. Due to the non-zero fluid parameters, the predictions of the effective field theory agree with observation much more accurately than standard perturbation theory and we explain why. We also discuss corrections from treating dark matter as interacting or wave-like and other issues.

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