Constraining nonthermal dark matter’s impact on the matter power spectrum
Constraining nonthermal dark matter’s impact on the matter power spectrum
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DOI：
10.1103/physrevd.100.123520
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发表时间：
2019-08
影响因子：
5
通讯作者：
Carisa Miller;A. Erickcek;R. Murgia
中科院分区：
文献类型：
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作者：
Carisa Miller;A. Erickcek;R. Murgia
在膨胀之后和辐射支配开始之前，包括一段(有效的)物质支配时期，对结构增长具有有趣和可观察的后果。在这个早期的物质主宰时代(Emde)，宇宙被大质量粒子或振荡的标量场所主导，这些粒子衰变成标准模型粒子，从而重新加热宇宙。这种衰变过程也可能是暗物质的主要来源。在母粒子和子粒子的质量之间没有微调的情况下，暗物质粒子和标准模型粒子都将以相对论速度产生。通过确定暗物质的速度分布函数，研究了具有相对论速度的暗物质粒子的非热产生对物质功率谱的影响。我们发现，在Emde期间产生的绝大多数暗物质粒子在重新加热时仍然是相对论的，所以它们的自由流动消除了Emde期间增长的微扰。暗物质粒子的自由流动也可以防止银河系周围卫星星系的形成，以及莱曼-阿尔法森林中观察到的结构。对于给定的再加热温度，这些观测结果为暗物质粒子的产生设定了速度上限。例如，对于10 MeV的再热温度，暗物质的产生必须具有洛伦兹因子$\γ\less sim 550$。
The inclusion of a period of (effective) matter domination following inflation and prior to the onset of radiation domination has interesting and observable consequences for structure growth. During this early matter-dominated era (EMDE), the Universe was dominated by massive particles, or an oscillating scalar field, that decayed into Standard Model particles, thus reheating the Universe. This decay process could also be the primary source of dark matter. In the absence of fine-tuning between the masses of the parent and daughter particles, both dark matter particles and Standard Model particles would be produced with relativistic velocities. We investigate the effects of the nonthermal production of dark matter particles with relativistic velocities on the matter power spectrum by determining the resulting velocity distribution function for the dark matter. We find that the vast majority of dark matter particles produced during the EMDE are still relativistic at reheating, so their free streaming erases the perturbations that grow during the EMDE. The free streaming of the dark matter particles can also prevent the formation of satellite galaxies around the Milky Way and the structures observed in the Lyman-$\alpha$ forest. For a given reheat temperature, these observations put an upper limit on the velocity of the dark matter particles at their creation. For example, for a reheat temperature of 10 MeV, dark matter must be produced with a Lorentz factor $\gamma \lesssim 550$.