连续量子蒙特卡罗计算中的二阶微扰理论
Second-Order Perturbation Theory in Continuum Quantum Monte Carlo Calculations
AI总结：
本研究将二阶能量修正计算映射为扩散蒙特卡罗方法的虚时演化，首次在连续量子蒙特卡罗框架下实现核多体系统基态能量的二阶微扰修正计算，验证了方法有效性并揭示核相互作用的微扰特性，方法普适性强。
摘要：
我们报道了在连续量子蒙特卡罗计算中，对核多体系统基态能量进行二阶微扰理论修正的首批结果。在大多数从头算多体方法中，二阶（及更高阶）微扰修正的计算难度极大，这类方法通常聚焦于获取基态能量。通过将我们的二阶能量修正计算映射为使用扩散蒙特卡罗方法的虚时演化过程，我们首次得以计算这些核修正项。在少体领域对方法进行基准测试后，我们探究了核哈密顿量中电荷无关性破缺项的效应。随后我们采用该方法研究了多体微扰的逐阶收敛性，这一特性在源自手征有效场论的现代核子-核子相互作用理论中具有核心意义。我们发现，更高手征阶的势之间存在依赖于截断的微扰性，且领头阶与次领头阶势之间的差异具有非微扰性；这两项结果对未来的核多体计算均具有重要意义。我们的方法具有相当的普适性，有望得到广泛应用。
英文摘要：
We report on the first results for the second-order perturbation theory correction to the ground-state energy of a nuclear many-body system in a continuum quantum Monte Carlo calculation. Second-order (and higher) perturbative corrections are notoriously difficult to compute in most ab initio many-body methods, where the focus is usually on obtaining the ground-state energy. By mapping our calculation of the second-order energy correction to an evolution in imaginary time using the diffusion Monte Carlo method, we are able to calculate these nuclear corrections for the first time. After benchmarking our method in the few-body sector, we explore the effect of charge-independence-breaking terms in the nuclear Hamiltonian. We then employ that approach to investigate the many-body, perturbative, order-by-order convergence that is fundamental in modern theories of the nucleon-nucleon interaction derived from chiral effective field theory. We find cutoff-dependent perturbativeness between potentials at higher chiral order and also that the difference between leading order and next-to-leading order potentials is nonperturbative; both of these results have important implications for future nuclear many-body calculations. Our approach is quite general and promises to be of wide applicability.
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