标题： 三中子共振的能量是否低于四中子共振？ 显示英文标题

标题： Is a Trineutron Resonance Lower in Energy than a Tetraneutron Resonance?

摘要： 我们展示了基于局域有效场论中次次领头阶χEFT相互作用的受限于外部势的少中子系统量子蒙特卡罗计算。这些系统的能量和径向密度被计算在不同的外 Woods-Saxon 势中。我们假设它们外势深度趋近于零时的外推可以定量估算三中子和四中子共振。通过两体情况下的精确对角化验证了这个假设的有效性。我们发现外推得到的三中子共振以及浅阱深度的能量比四中子共振能量低。这表明在自然界中四中子共振之下存在一个三中子共振，并且可能被测量到。为了确认三中子和四中子共振的相对顺序不是外部约束的伪影，我们测试了氦同位素链中的奇偶交错在这个方法中是否被再现。最后，我们讨论了我们的结果与超冷费米气体之间的相似之处。 显示英文摘要

摘要： We present quantum Monte Carlo calculations of few-neutron systems confined in external potentials based on local chiral interactions at next-to-next-to-leading order in chiral effective field theory. The energy and radial densities for these systems are calculated in different external Woods-Saxon potentials. We assume that their extrapolation to zero external-potential depth provides a quantitative estimate of three- and four-neutron resonances. The validity of this assumption is demonstrated by benchmarking with an exact diagonalization in the two-body case. We find that the extrapolated trineutron resonance, as well as the energy for shallow well depths, is lower than the tetraneutron resonance energy. This suggests that a three-neutron resonance exists below a four-neutron resonance in nature and is potentially measurable. To confirm that the relative ordering of three- and four-neutron resonances is not an artifact of the external confinement, we test that the odd-even staggering in the helium isotopic chain is reproduced within this approach. Finally, we discuss similarities between our results and ultracold Fermi gases.