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arXiv 1802.06589astro-ph.CO
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符合普朗克数据精度的$γ$ - CDM相互作用的约束

Constraints on $γ$-CDM interactions matching the Planck data precision

Julia Stadler, Céline Bœhm

摘要:

普朗克实验以前所未有的精度测量了宇宙微波背景(CMB)角谱,这些结果可能在十年或更长时间内保持最先进水平。由于这些测量将被用来预测欧几里德的能力,以测试替代暗物质模型,我们的目标是在早期宇宙中的暗物质-光子散射的截面上设置最终的CMB约束。由于形式主义尚未在文献中发表,我们提出的关键步骤,推导出完整的线性化爱因斯坦和玻尔兹曼方程,并阐明必要的修改视线和紧耦合近似。这些近似方案通常用于玻尔兹曼代码,以减少计算成本,但紧耦合制度已被忽略在以前的工作有关的暗物质-光子相互作用。我们的计算考虑了暗物质的声速,这在以前的工作中被忽略了。我们发现它对CMB谱的影响可以忽略不计,但对线性物质功率谱的影响相当大。然后,我们分析了普朗克数据,有和没有2015年的极化数据在高多极。在这两种情况下,我们对弹性散射截面与暗物质质量之比的约束相对于以前的约束变得更加严格。当加入完整的Planck数据集(包括高多极子下的E模偏振和透镜势功率谱)时,变化约为35%,当加入完整的Planck数据集(包括高多极子下的E模偏振和透镜势功率谱)时变化约为20%。当我们只考虑在低多极和全温度谱的偏振数据时。我们最保守的限值读数为$σ_{\mathrm{DM}-γ} \leq 2.25\times 10^{-6}\,σ_\mathrm{Th}\left(m_\mathrm{DM}/\mathrm{GeV}\right)$,置信度为95\%。我们不希望通过添加最近公布的SPT数据来改变这一限制。

英文摘要:

The Planck experiment has measured the Cosmic Microwave Background (CMB) angular spectrum with unprecedented accuracy, and these results are likely to remain the state-of-the art for a decade or more. Since these measurements are going to be used to forecast Euclid's ability to test alternative dark matter models, we aim to set the final CMB constraint on the cross section of dark matter-photon scattering in the early universe. As the formalism has not been published in the literature yet, we present the key steps to derive the full set of linearized Einstein and Boltzmann equations and elucidate necessary modifications to the line of sight and the tight coupling approximation. These approximation schemes are commonly used in Boltzmann codes to reduce computational costs, but the tight coupling regime has been neglected in previous works related to dark matter-photon interactions. Our computations account for a dark matter sound speed, which was neglected in previous work. We find that its effect is negligible on the CMB spectra but fairly important on the linear matter power spectrum. We then analyze the Planck data, with and without the 2015 polarization data at high multipoles. In both cases our constraint on the ratio of the elastic scattering cross section to the dark matter mass becomes more stringent with respect to previous constraints. The change is about 35\% when the full Planck dataset is added (which includes E-mode polarization at high multipoles and the lensing potential power spectrum) and about 20\%. when we only account for the polarization data at low multipoles and the full temperature spectrum. Our most conservative limit reads as $σ_{\mathrm{DM}-γ} \leq 2.25\times 10^{-6}\,σ_\mathrm{Th}\left(m_\mathrm{DM}/\mathrm{GeV}\right)$ at 95\% confidence. We do not expect this limit to change by adding the recently published SPT data.

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