Growth of dark matter perturbations during kination
Growth of dark matter perturbations during kination
复制标题
运动过程中暗物质扰动的增长
作者：
Kayla Redmond;Anthony Trezza;A. Erickcek
如果宇宙的能量密度由快速滚动的标量场主导，而辐射浴足够热以产生暗物质，那么具有大于正则湮灭截面的暗物质可以产生观测到的暗物质遗迹丰度。为了进一步限制这些情况下，我们调查的小规模的密度扰动在这样一个时期的kination的演变。我们确定，一旦微扰模式进入视界在kinination，引力势急剧下降，并开始振荡和衰减。然而，暗物质的密度扰动，进入视界在一个时代的kination线性增长的比例因子开始之前的辐射优势。因此，动能在物质的功率谱上留下了独特的印记：在动能过程中进入视界的尺度增强了不均匀性。我们还考虑如何物质密度扰动时，宇宙的主要组成部分有一个通用的状态方程参数$w$的演变。我们发现，物质密度扰动不增长，如果他们进入视界时，${0 1/3}$，他们的增长速度比辐射支配期间经历的对数增长。由此产生的小尺度物质功率谱的提升导致了增强子结构的形成，这有效地增加了暗物质的湮灭率，并可能使热暗物质的产生与观测不相容。
If the Universe's energy density was dominated by a fast-rolling scalar field while the radiation bath was hot enough to thermally produce dark matter, then dark matter with larger-than-canonical annihilation cross sections can generate the observed dark matter relic abundance. To further constrain these scenarios, we investigate the evolution of small-scale density perturbations during such a period of kination. We determine that once a perturbation mode enters the horizon during kination, the gravitational potential drops sharply and begins to oscillate and decay. Nevertheless, dark matter density perturbations that enter the horizon during an era of kination grow linearly with the scale factor prior to the onset of radiation domination. Consequently, kination leaves a distinctive imprint on the matter power spectrum: scales that enter the horizon during kination have enhanced inhomogeneity. We also consider how matter density perturbations evolve when the dominant component of the Universe has a generic equation-of-state parameter $w$. We find that matter density perturbations do not grow if they enter the horizon when ${0 1/3}$, their growth is faster than the logarithmic growth experienced during radiation domination. The resulting boost to the small-scale matter power spectrum leads to the formation of enhanced substructure, which effectively increases the dark matter annihilation rate and could make thermal dark matter production during an era of kination incompatible with observations.
影响因子：
4.4
作者：
Adam J. Christopherson;Karim A. Malik
通讯作者：
Adam J. Christopherson;Karim A. Malik