早期物质支配的最小遗迹
Smallest Remnants of Early Matter Domination
摘要：
在大爆炸核合成之前的宇宙演化可能经历了早期物质支配（EMD）阶段，这增强了小尺度暗物质结构的生长。如果EMD足够长，自引力物体在重新加热之前形成。我们研究了这些密集的早期晕（EH）通过再加热的演变。在EMD结束时，EH经历快速膨胀并最终喷射出它们的物质。我们发现，这个过程冲洗出的结构尺度比原始晕的尺寸天真地预期的要大得多。我们计算的EH残留物的密度分布，并使用它们来构建后期的功率谱，包括这些非线性效应。EH动力学限制了EMD以独立于暗物质微观物理的方式产生的最大增强。我们发展了一个外推的$Λ$ CDM功率谱，以估计物质辐射相等后形成的微晕的性质。令人惊讶的是，宇宙学与短周期的EMD导致更早的微晕形成相比，那些与一个长周期的EMD。无论哪种情况，暗物质结构的形成都比标准宇宙学早得多，大多数暗物质都被束缚在微晕中。
英文摘要：
The evolution of the universe prior to Big Bang Nucleosynthesis could have gone through a phase of early matter domination (EMD) which enhanced the growth of small-scale dark matter structure. If EMD was long enough, self-gravitating objects formed prior to reheating. We study the evolution of these dense early halos (EHs) through reheating. At the end of EMD, EHs undergo rapid expansion and eventually eject their matter. We find that this process washes out structure on scales much larger than naively expected from the size of the original halos. We compute the density profiles of the EH remnants and use them to construct late-time power spectra that include these non-linear effects. EH dynamics limits the maximum enhancement that can be generated by EMD in a way that is independent of the dark matter microphysics. We evolve an extrapolated $Λ$CDM power spectrum to estimate the properties of microhalos that would form after matter-radiation equality. Surprisingly, cosmologies with a short period of EMD lead to an earlier onset of microhalo formation compared to those with a long period of EMD. In either case, dark matter structure formation begins much earlier than in the standard cosmology, with most DM bound in microhalos.
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