arXiv 1909.004882019-09astro-ph.CO

束缚暗物质（BDM）解决小尺度结构问题

Bound Dark Matter (BDM) towards solving the Small Scale Structure Problem

Jorge Mastache, Axel de la Macorra

备注：: 24 pages, 10 figues
DOI：: 10.1088/1475-7516/2020/03/025

摘要：

结构形成、宇宙微波背景辐射和宇宙距离阶梯等宇宙学观测对暗物质的数量和性质提出了严格的限制。特别地，结构的形成不仅强烈地限制了能量密度的大小，而且还限制了DM变为非相对论性的时间。标准的冷和热的DM粒子有一个平稳的过渡，从相对论性在高能量的非相对论性制度，因为这些粒子的质量是恒定的，而速度红移与宇宙的膨胀。然而，在这里，我们探讨的可能性，DM粒子获得非微扰质量在相变规模和比例因子ac。这种转变对于束缚暗物质（BDM）模型来说具有更基本的意义，因为它们描述了粒子通过非微扰过程获得质量。这些BDM粒子可能在ac处从相对论性转变为非相对论性，这意味着粒子速度vc在那时的突然转变，影响状态方程和宇宙学演化。在这里，我们研究的宇宙学影响的价值观的vc和标度转换ac和他们通过减少自由流动的规模，因此，小尺度结构。使用CMB普朗克，超新星SNIa，和BAO数据，我们约束的有效区域在参数空间AC-VC把上限AC，但不限制VC。例如，对于vc = 0，转换必须为ac< $2.66\times10^{-6}$。我们还发现，速度vc对暗物质粒子的自由流动和Jeans质量有很大的影响，例如，一个3 keV的WDM粒子的Jeans质量为Mfs= $1.97\times10^7$ Msun/h^3，而一个等效的BDM粒子的Jeans质量为Mfs= $2.08x10^4$ Msun/h^3，速度vc~0的变化会显著改变大尺度结构的形成.

英文摘要：

Cosmological observations such as structure formation, CMB, and cosmic distance ladder set tight constraints to the amount and nature of dark matter (DM). In particular structure formation strongly constraints not only the amount of energy density, but also the time when DM became non-relativistic, anr. Standard cold and thermic warm DM particles have a smooth transition from being relativistic at high energies to a non-relativistic regime since the mass of these particles is constant while the velocity redshifts with the expansion of the universe. However, here we explore the possibility that the DM particle acquires a non-perturbative mass at a phase transition scale and a scale factor ac. This transition acquired a more fundamental meaning for the Bound Dark Matter (BDM) model because they describe a particle getting its mass through a non-perturbative process. These BDM particles may go from being relativistic to non-relativistic at ac, which implies an abrupt transition of the velocity of the particles vc at that time, affecting the equation of state and the cosmological evolution. Here we study the cosmological impact of the values of vc and the scale transition ac and they by reducing the free-streaming scale and therefore the small scale structure. Using CMB Plank, Supernovae SNIa, and BAO data, we constrain the valid region in the parameter space ac-vc putting upper bounds to ac but not restricting vc. For instance, the transition must be ac<$2.66\times10^{-6}$ for vc = 0. We also find that the free-streaming and the Jeans mass of the dark matter particle is highly influenced by the velocity vc, for example, a 3 keV WDM have a Jeans mass of Mfs=$1.97\times10^7$ Msun/h^3 but an equivalent BDM with the same anr but an abrupt transition in the velocity, vc~0 would have a Jeans mass of Mfs=$2.08x10^4$ Msun/h^3 which significantly changes the large scale structure formation.

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