We investigate the impact of the QCD vacuum at nonzero $\theta$ on the properties of light nuclei, Big Bang nucleosynthesis, and stellar nucleosynthesis. Our analysis starts with a calculation of the $\theta$-dependence of the neutron-proton mass difference and neutron decay using chiral perturbation theory. We then discuss the $\theta$-dependence of the nucleon-nucleon interaction using a one-boson-exchange model and compute the properties of the two-nucleon system. Using the universal properties of four-component fermions at large scattering length, we then deduce the binding energies of the three-nucleon and four-nucleon systems. Based on these results, we discuss the implications for primordial abundances of light nuclei, the production of nuclei in stellar environments, and implications for an anthropic view of the universe.

中文翻译：

---

轻核与核合成的θ依赖性

我们调查了非零时QCD真空的影响 $\theta$轻核，大爆炸核合成和恒星核合成的性质。我们的分析始于对$\theta$-利用手性摄动理论对中子-质子质量差和中子衰变的依赖性。然后，我们讨论$\theta$-使用一玻色子交换模型对核子-核子相互作用的依赖性，并计算两核子系统的性质。利用四组分费米子在大散射长度下的通用性，我们推论了三核子和四核子系统的结合能。基于这些结果，我们讨论了对轻核原始丰度的影响，恒星环境中核的产生以及对宇宙人类观的影响。