论文标题

热核反应速率和原始核合成

Thermonuclear reaction rates and primordial nucleosynthesis

论文作者

Iliadis, Christian, Coc, Alain

论文摘要

假设具有宇宙性重子密度的最佳数值和三种中微子风味的存在,则标准的大爆炸核合成是一个无参数的模型。重要的是要评估观察到的原始丰度是否可以通过模拟复制。大量研究表明,与观察值相比,模拟预测原始$^7 $ li的丰度约为$ 3 $。差异可能是由于$^7 $ li观察值的未知系统学,恒星中锂的耗竭,热核速率的误解,热核速率的错误参与锂和铍的合成,或者是标准模型以外的物理学。在这里,我们专注于核物理解决方案的可能性。总结了主要的核反应率的状态。大爆炸核合成模拟以最新的反应速率进行,并使用蒙特卡洛技术建立了预测丰度的不确定性。根据相互信息的度量,研究了丰度与反应率之间的相关性。四个反应的费率影响原始$^7 $ li丰富:$^3 $ he($α$,$γ$)$^7 $ be,d(p,$γ$)$^3 $ he,$^7 $ be(d,d,p)2 $α$,$^7 $ be(n,p)$^7 $^7 $^7 $ li。我们采用遗传算法来寻找这四种反应的同时速率变化,这可能解释了所有观察到的原始丰度。当对反应速率范围进行搜索比最近报道的不确定性宽得多时,找不到可接受的解决方案。根据当前可用的证据,我们得出结论,具有核物理解决方案的宇宙学问题极不可能。

Assuming the best numerical value for the cosmic baryonic density and the existence of three neutrino flavors, standard big bang nucleosynthesis is a parameter-free model. It is important to assess if the observed primordial abundances can be reproduced by simulations. Numerous studies have shown that the simulations overpredict the primordial $^7$Li abundance by a factor of $\approx$ $3$ compared to the observations. The discrepancy may be caused by unknown systematics in $^7$Li observations, poorly understood depletion of lithium in stars, errors in thermonuclear rates that take part in the lithium and beryllium synthesis, or physics beyond the standard model. Here, we focus on the likelihood of a nuclear physics solution. The status of the key nuclear reaction rates is summarized. Big bang nucleosynthesis simulations are performed with the most recent reaction rates and the uncertainties of the predicted abundances are established using a Monte Carlo technique. Correlations between abundances and reaction rates are investigated based on the metric of mutual information. The rates of four reactions impact the primordial $^7$Li abundance: $^3$He($α$,$γ$)$^7$Be, d(p,$γ$)$^3$He, $^7$Be(d,p)2$α$, and $^7$Be(n,p)$^7$Li. We employ a genetic algorithm to search for simultaneous rate changes in these four reactions that may account for all observed primordial abundances. When the search is performed for reaction rate ranges that are much wider than recently reported uncertainties, no acceptable solutions are found. Based on the currently available evidence, we conclude that it is highly unlikely for the cosmological lithium problem to have a nuclear physics solution.

扫码加入交流群

加入微信交流群

微信交流群二维码

扫码加入学术交流群,获取更多资源