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arXiv 1906.00730astro-ph.COgr-qc
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动力学和势自相互作用对标量暗物质的影响

Impact of kinetic and potential self-interactions on scalar dark matter

Philippe Brax, Jose A. R. Cembranos, Patrick Valageas

摘要:

我们考虑模型的标量暗物质与一个通用的相互作用势和非典型的K-本质类型的动力学项是subleading相对于典型的长期。我们分析了低能量的制度,并推导出,在非相对论性的限制,有效的运动方程。在流体近似中,它们归结为物质守恒和速度场的欧拉方程。我们专注于的情况下,标量场质量$10^{-21} \ll m \lesssim 10^{-4} \, {\rm eV}$是远远大于模糊暗物质,使量子压力是可以忽略不计的宇宙学和银河系尺度,而自相互作用势和非正则动力学项产生显着的排斥压力。在宇宙学扰动的水平上,这提供了暗物质密度依赖的声速。在非线性水平上,通过平衡引力和标量相互作用获得的流体静力学平衡意味着维里化结构具有有限大小的孤子核心,其大小取决于暗物质流体的声速。对于具有$(\partial ϕ)^4$相互作用的$λ_4 ϕ^4/4$或K-本质中最相关的势能,这种稳定核的大小不能超过60 kpc。密度对比度大于$10^6$的结构可与声速$c_s\lesssim 10^{-6}$相适应。我们还考虑了余弦自相互作用的情况下,作为有界非多项式自相互作用的一个例子。这在低质量和低密度晕中给出了类似的结果,而在大质量晕中没有孤波核。

英文摘要:

We consider models of scalar dark matter with a generic interaction potential and non-canonical kinetic terms of the K-essence type that are subleading with respect to the canonical term. We analyze the low-energy regime and derive, in the nonrelativistic limit, the effective equations of motions. In the fluid approximation they reduce to the conservation of matter and to the Euler equation for the velocity field. We focus on the case where the scalar field mass $10^{-21} \ll m \lesssim 10^{-4} \, {\rm eV}$ is much larger than for fuzzy dark matter, so that the quantum pressure is negligible on cosmological and galactic scales, while the self-interaction potential and non-canonical kinetic terms generate a significant repulsive pressure. At the level of cosmological perturbations, this provides a dark-matter density-dependent speed of sound. At the nonlinear level, the hydrostatic equilibrium obtained by balancing the gravitational and scalar interactions imply that virialized structures have a solitonic core of finite size depending on the speed of sound of the dark matter fluid. For the most relevant potential in $λ_4 ϕ^4/4$ or K-essence with a $(\partial ϕ)^4$ interaction, the size of such stable cores cannot exceed 60 kpc. Structures with a density contrast larger than $10^6$ can be accommodated with a speed of sound $c_s\lesssim 10^{-6}$. We also consider the case of a cosine self-interaction, as an example of bounded nonpolynomial self-interaction. This gives similar results in low-mass and low-density halos whereas solitonic cores are shown to be absent in massive halos.

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