权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Nucleosynthesis in the Early Universe and the test of Big Bang Model

早期宇宙的核合成与大爆炸模型的检验

基本信息

批准号：
07640386
负责人：
SATO Katsuhiko
金额：
$ 1.41万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

Standard big bang cosmology gives us a simple and natural picture of our universe since it explains the origin of cosmic microwave background and abundances of light elements, ^4He, D,^3He and ^7Li. The standard big bang nucleosynthesis (SBBN) has a single free parameter, i.e. baryon to photon number ratio eta=n_B/n_<gamma> where n_B and n_<gamma> are the number densities of baryons and photons. Comparing SBBN predictions with abundances of light elements inferred from observational data, we obtain the baryon density of the universe, OMEGA_b<approximately equal>0.01.Recently, however, it is reported that there is the discrepancy between big bang nucleosynthesis theory and observations (BBN crisis). We show that BBN predictions agree with the primordial abundances of light elements, ^4He, D,^3He and ^7Li inferred from the observational data if an electron neutrino has a net chemical potential xi_<nue> due to lepton asymmetry. We estimated that xi_<nue>=0.043^<+0.040>_<040> (95% C.L.) and OMEGA_bh^2=0.015^<+0.006>_<003> (95% C.L.). We also investigated in detail nucleosynthesis in inhomogeneous universe model, and confirmed that essentially the constraint on the baryon to photon number ratio from light element observations is the same as that of standard model, since the observation of Li gives stringent limit to the density contrast of the inhomogeneity.

标准的大爆炸宇宙学解释了宇宙微波背景辐射的起源以及轻元素^4 He、D、^3 He和^7 Li的丰度，因此为我们提供了一幅简单而自然的宇宙图景。标准大爆炸核合成（SBBN）只有一个自由参数，即重子与光子数比η =n_B/n_<gamma>，其中n_B和n_分别<gamma>是重子和光子的数密度。将SBBN预言与由观测数据推断的轻元素丰度进行比较，我们得到了宇宙的重子密度OMEGA_B <approximately equal>0.01。然而，最近有报道称，大爆炸核合成理论与观测存在偏差（BBN危机）。我们证明，如果电子中微子由于轻子不对称性而具有净化学势xi，则BBN预言与根据观测数据推断的轻元素^4He、D、^3He和^7Li的原始丰度是一致<nue>的。我们估计x1_<nue>=0.043^<+0.040>_<040>（95% C.L.）Ω_bh^2 =0.015^<+0.006>_<003>（95% C.L.）。我们还详细地研究了非均匀宇宙模型中的核合成，证实了由于Li的观测对非均匀性的密度衬度给出了严格的限制，因此从轻元素观测中得到的重子光子数比的约束与标准模型中的重子光子数比的约束基本上是相同的。