arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0906.3880astro-ph.COgr-qchep-ph
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第五种力I的结构形成:N体与线性模拟

Structure Formation by Fifth Force I: N-Body vs. Linear Simulations

Baojiu Li, Hongsheng Zhao

摘要:

我们给出了一般暗物质耦合标量场模型中线性和非线性结构形成的数值研究框架,并给出了一个明确的例子,其中标量场作为一个动态的暗能量。采用标量场的参数,产生一个现实的CMB谱,我们产生的初始条件,我们的N体模拟,其中遵循的空间分布的暗物质和标量场的运动方程求解使用多级自适应网格技术。我们发现,空间配置的标量场跟踪以及空洞和集群的暗物质。事实上,标量自由度的传播有效地对暗物质粒子施加了第五种力,其范围和大小由两个模型参数(μ、γ)、局部暗物质密度以及标量场的背景值决定。该模型的行为就像LCDM范式的尺度相关的CMB频谱,这是远远超出了本地第五力的探针,因此没有显着影响的物质标量耦合。如果变色龙效应较弱,在与局域第五力的范围相当或比其范围更短的尺度上,第五力与引力完全平行,它们的强度具有由物质-标量耦合决定的固定比值2 γ ^2;另一方面,如果存在较强的变色龙效应(即,标量场几乎在空间中的任何地方都处于其有效势最小值),第五种力确实在高密度区域具有抑制效应,并且没有显示出与重力的明显相关性,这意味着暗物质-标量场耦合并不简单地等效于引力常量或暗物质粒子质量的重新标度。

英文摘要:

We lay out the frameworks to numerically study the structure formation in both linear and nonlinear regimes in general dark-matter-coupled scalar field models, and give an explicit example where the scalar field serves as a dynamical dark energy. Adopting parameters of the scalar field which yield a realistic CMB spectrum, we generate the initial conditions for our N-body simulations, which follow the spatial distributions of the dark matter and the scalar field by solving their equations of motion using the multilevel adaptive grid technique. We show that the spatial configuration of the scalar field tracks well the voids and clusters of dark matter. Indeed, the propagation of scalar degree of freedom effectively acts a fifth force on dark matter particles, whose range and magnitude are determined by the two model parameters (mu, gamma), local dark matter density as well as the background value for the scalar field. The model behaves like the LCDM paradigm on scales relevant to the CMB spectrum, which are well beyond the probe of the local fifth force and thus not significantly affected by the matter-scalar coupling. On scales comparable or shorter than the range of the local fifth force, the fifth force is perfectly parallel to gravity and their strengths have a fixed ratio 2gamma^2 determined by the matter-scalar coupling, provided that the chameleon effect is weak; if on the other hand there is a strong chameleon effect (i.e., the scalar field almost resides at its effective potential minimum everywhere in the space), the fifth force indeed has suppressed effects in high density regions and shows no obvious correlation with gravity, which means that the dark-matter-scalar-field coupling is not simply equivalent to a rescaling of the gravitational constant or the mass of the dark matter particles.

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