The Dark Matter Annihilation Boost from Low-Temperature Reheating
The Dark Matter Annihilation Boost from Low-Temperature Reheating
复制标题
低温再加热促进暗物质湮灭
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
A. Erickcek
中科院分区：
文献类型：
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作者：
A. Erickcek
宇宙在暴胀和大爆炸核合成开始之间的演化是很难探测的，而且在很大程度上是不受约束的。这种无知极大地限制了我们对暗物质的理解：如果不知道宇宙何时成为辐射主导的，我们就无法计算它的热遗迹丰度。幸运的是，小尺度的密度扰动提供了一种对早期宇宙的探测，可以打破这种简并性。如果暗物质是热遗迹，那么在早期物质主导时代进入视界的密度扰动在再加热之前随着比例因子线性增长。由此产生的丰富的子结构将湮灭率提高了几个数量级，这可以补偿在这些场景中产生观测到的暗物质密度所需的较小湮灭截面。特别是，热遗迹与质量小于TeV的热和动力学去耦再加热之前可能已经排除了费米-LAT观测矮球状星系。虽然这些限制受到微晕内部结构的不确定性的影响，这些微晕是由增强的扰动形成的，但它们开辟了使用伽马射线观测来了解宇宙再加热的可能性。
The evolution of the Universe between inflation and the onset of big bang nucleosynthesis is difficult to probe and largely unconstrained. This ignorance profoundly limits our understanding of dark matter: we cannot calculate its thermal relic abundance without knowing when the Universe became radiation dominated. Fortunately, small-scale density perturbations provide a probe of the early Universe that could break this degeneracy. If dark matter is a thermal relic, density perturbations that enter the horizon during an early matter-dominated era grow linearly with the scale factor prior to reheating. The resulting abundance of substructure boosts the annihilation rate by several orders of magnitude, which can compensate for the smaller annihilation cross sections that are required to generate the observed dark matter density in these scenarios. In particular, thermal relics with masses less than a TeV that thermally and kinetically decouple prior to reheating may already be ruled out by Fermi-LAT observations of dwarf spheroidal galaxies. Although these constraints are subject to uncertainties regarding the internal structure of the microhalos that form from the enhanced perturbations, they open up the possibility of using gamma-ray observations to learn about the reheating of the Universe.