Structural phenomena in nuclei, from shell structure and clustering to superfluidity and collective rotations and vibrations, reflect emergent degrees of freedom. Ab initio theory describes nuclei directly from a fully microscopic formulation. We can therefore look to ab initio theory as a means of exploring the emergence of effective degrees of freedom in nuclei. For the illustrative case of emergent rotational bands in the \(\hbox {Be}\) isotopes, we establish an understanding of the underlying oscillator space and angular momentum (orbital and spin) structure. We consider no-core configuration interaction (NCCI) calculations for with the Daejeon16 internucleon interaction. Although shell model or rotational degrees of freedom are not assumed in the ab initio theory, the NCCI results are suggestive of the emergence of effective shell model degrees of freedom ( and excitations) and LS-scheme rotational degrees of freedom, consistent with an Elliott–Wilsdon description. These results provide some basic insight into the connection between emergent effective collective rotational and shell model degrees of freedom in these light nuclei and the underlying ab initio microscopic description.

中文翻译：

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探索核循环的从头开始出现

原子核中的结构现象，从壳结构和团簇到超流体以及集体旋转和振动，反映了新兴的自由度。从头算理论直接从完全微观的公式描述了原子核。因此，我们可以将从头算理论视为探索核中有效自由度出现的一种手段。对于\（\ hbox {Be} \）同位素中出现的旋转带的说明性情况，我们建立了对潜在的振荡器空间和角动量（轨道和自旋）结构的理解。我们考虑以下情况的无核心配置交互（NCCI）计算：与Daejeon16核仁相互作用。尽管从头算没有假设壳模型或旋转自由度，但NCCI结果表明出现了有效的壳模型自由度（和激发）和LS方案旋转自由度，与Elliott- Wilsdon描述。这些结果为这些轻核中出现的有效集体旋转自由度和壳模型自由度之间的联系以及从头开始的微观描述之间的联系提供了一些基本的见识。