多体展开法的自然轨道
Natural orbitals for many-body expansion methods
摘要：
中等质量系统的核多体问题通常使用波函数展开方法来解决，该方法建立在多体算子相对于所选计算基础的二次量化表示的基础上。虽然各种选择的计算基础，扰动构造的自然轨道最近已被证明导致显着改善多体应用产生更快的模型空间收敛和更低的灵敏度，在大规模的无核壳模型对角化的基组参数。这项工作提供了一个详细的比较单粒子基组和系统的基准的自然轨道在非微扰多体计算中使用的介质相似性重整化群的方法。作为一个关键的结果，我们发现，在一个大的单粒子基础上的自然轨道的建设，使执行多体计算在一个减少的空间低得多的维度，从而提供显着的计算节省在实践中，有助于扩展从头算方法的范围向更重的质量和更高的精度。
英文摘要：
The nuclear many-body problem for medium-mass systems is commonly addressed using wave-function expansion methods that build upon a second-quantized representation of many-body operators with respect to a chosen computational basis. While various options for the computational basis are available, perturbatively constructed natural orbitals recently have been shown to lead to significant improvement in many-body applications yielding faster model-space convergence and lower sensitivity to basis set parameters in large-scale no-core shell model diagonalizations. This work provides a detailed comparison of single-particle basis sets and a systematic benchmark of natural orbitals in nonperturbative many-body calculations using the in-medium similarity renormalization group approach. As a key outcome we find that the construction of natural orbitals in a large single-particle basis enables for performing the many-body calculation in a reduced space of much lower dimension, thus offering significant computational savings in practice that help extend the reach of ab initio methods towards heavier masses and higher accuracy.
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