开壳层核谱的Padé恢复简并微扰理论
Spectra of Open-Shell Nuclei with Padé-Resummed Degenerate Perturbation Theory
摘要：
本文应用高阶简并多体微扰理论，利用软现实核子-核子相互作用，对开壳层核的基态和激发谱进行了从头计算。我们推导出一个递归制定的标准简并多体微扰理论，使我们能够评估订单的顺序微扰能量和状态修正到第30阶。利用手征有效场论中的相似重整化群（SRG）演化的核子-核子相互作用，我们研究了6，7-Li的核反应.简单的微扰级数表现出强烈的，往往是振荡的发散，如以前观察到的基态的封闭壳层核。即使对于由SRG演化到大流动参数（即低动量尺度）所产生的非常软的相互作用，扰动序列仍然发散。然而，通过Padé近似的微扰序列的remmation产生非常稳定和收敛的基态和激发态能量，与相同模型空间的精确无核壳模型计算非常一致。
英文摘要：
We apply degenerate many-body perturbation theory at high orders for the ab-initio description of ground states and excitation spectra of open-shell nuclei using soft realistic nucleon-nucleon interactions. We derive a recursive formulation of standard degenerate many-body perturbation theory that enables us to evaluate order-by-order perturbative energy and state corrections up to the 30th order. We study 6,7-Li as test cases using a similarity renormalization group (SRG) evolved nucleon-nucleon interaction from chiral effective field theory. The simple perturbation series exhibits a strong, often oscillatory divergence, as was observed previously for ground states of closed-shell nuclei. Even for very soft interactions resulting from SRG evolutions up to large flow parameter, i.e. low momentum scales, the perturbation series still diverges. However, a resummation of the perturbation series via Padé approximants yields very stable and converged ground and excited-state energies in very good agreement with exact no-core shell-model calculations for the same model space.
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