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arXiv 2011.10937astro-ph.CO
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临界坍缩模型中原初黑洞的霍金辐射对轻元素丰度的影响

Impacts of Hawking Radiation from Primordial Black Holes in Critical Collapse Model on the Light Element Abundances

Yudong Luo, Chao Chen, Motohiko Kusakabe, Toshitaka Kajino

摘要:

在临界坍缩模型下研究了原初黑洞的非热电磁霍金辐射引发的光致蜕变过程。我们考虑最简单的情况下,所有的PBH形成在一个单一的时代起源于一个狭窄的峰值暴胀光谱,并得到一个扩展的质量分布,由于引力坍缩的临界现象。临界坍缩质量函数的低质量尾的存在可能导致PBH的霍金辐射的高能光子发射增强。用迭代求解玻尔兹曼方程得到的非热光子谱计算了核的光衰变率。精确的频谱是很大的不同,基于一个经常使用的分析弯曲的幂律谱,它被发现显着依赖于所采用的PBH质量函数。利用银河系H Ⅱ区$^3$ He丰度的最新观测极限,导出了视界质量范围$10^{12} - 10^{13}$ g内PBH质谱的最新$^3$ He约束.我们的结果首次表明,$^3$ He约束的临界质量函数是约一个数量级的单色的,虽然在低质量尾区的PBH的分数是相对较小的。对于临界质量函数,$^6$ Li元素丰度也显著增强。更精确地测量$^6$ Li丰度是非常期望的,以在未来提供对PBH的有希望的约束。对于单色质量函数,我们提供了PBH辐射的光衰变和强子解离的分析界限,并且我们报告了更新的$^3$ He约束与之前结果之间的差异。

英文摘要:

We study the photodisintegration process triggered by the nonthermal electromagnetic Hawking radiation from primordial black holes (PBHs) in critical collapse model. We consider the simplest case that all PBHs formed at a single epoch stemming from an inflationary spectrum with a narrow peak, and an extended mass distribution is obtained due to critical phenomena of gravitational collapse. The presence of a low-mass tail of critical collapse mass function could lead to an enhancement of energetic photon emissions from Hawking radiation of PBHs. Nuclear photodisintegration rates are calculated with a nonthermal photon spectrum derived by solving the Boltzmann equation iteratively. The exact spectrum is much different than that based on an often-used analytical bended power-law spectrum and it is found to significantly depend on the adopted PBH mass functions. With the newest observational limit on the $^3$He abundance in Galactic H II regions, the updated $^3$He constraints on PBH mass spectrum in the horizon mass range $10^{12} - 10^{13}$ g are derived. Our results for the first time show that $^3$He constraints on the critical mass function are about one order of magnitude severer than the monochromatic one although the fraction of PBHs in the low-mass tail region is relatively small. The $^6$Li elemental abundance is also enhanced significantly for the critical mass function. More precise measurement of $^6$Li abundance is highly desirable to provide a promising constraint on PBHs in the future. For monochromatic mass function, we provide the analytical bounds for photodisintegration and hadrodissociation from PBH radiation, and we report discrepancies between our updated $^3$He constraints and the previous results.

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