Nonthermal histories and implications for structure formation
Nonthermal histories and implications for structure formation
复制标题
非热历史和对结构形成的影响
DOI：
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
S. Watson
中科院分区：
文献类型：
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作者：
JiJi Fan;O. Ozsoy;S. Watson
我们研究了宇宙学扰动的演化在一个非热的后暴胀的历史与晚时间的BBN之前的物质统治时期。这样的宇宙学可以在超对称性（SUSY）背景下的动机良好的模量场景中自然出现-特别是在分裂-SUSY模型中。在再加热之前的物质主导阶段，亚视界暗物质扰动线性增长，并且即使在存在暗物质湮灭的情况下，也可以导致小尺度上的子结构增长的增强。这表明，一个新的尺度（再加热时的视界大小）对于确定原始物质的功率谱可能很重要。然而，我们发现，在许多非热模型的自由流效应或动力学解耦后，再加热可以完全消除增强导致小尺度结构。特别是，在wino或higgsino暗物质的模量方案中，我们发现从模量衰变产生的暗物质粒子将与辐射热化，并在再加热温度以下动力学解耦。因此，暗物质扰动的增长并不持续，对物质功率谱的预测与标准的热历史相似。我们对可能的例外情况进行了评论，但这些例外情况似乎很难在标准模数方案中实现。我们的结论是，虽然增强的结构并没有提供一个新的探针，在这些模型中的宇宙黑暗时代的调查，它确实表明，非热历史提供了一个强大的替代严格的热后暴胀的历史。
We examine the evolution of cosmological perturbations in a non-thermal post-inflationary history with a late-time matter domination period prior to BBN. Such a cosmology could arise naturally in the well-motivated moduli scenario in the context of supersymmetry (SUSY) -- in particular in models of Split-SUSY. Sub-horizon dark matter perturbations grow linearly during the matter dominated phase before reheating and can lead to an enhancement in the growth of substructure on small scales, even in the presence of dark matter annihilations. This suggests that a new scale (the horizon size at reheating) could be important for determining the primordial matter power spectrum. However, we find that in many non-thermal models free-streaming effects or kinetic decoupling after reheating can completely erase the enhancement leading to small-scale structures. In particular, in the moduli scenario with wino or higgsino dark matter we find that the dark matter particles produced from moduli decays would thermalize with radiation and kinetically decouple below the reheating temperature. Thus, the growth of dark matter perturbations is not sustained, and the predictions for the matter power spectrum are similar to a standard thermal history. We comment on possible exceptions, but these appear difficult to realize within standard moduli scenarios. We conclude that although enhanced structure does not provide a new probe for investigating the cosmic dark ages within these models, it does suggest that non-thermal histories offer a robust alternative to a strictly thermal post-inflationary history.