球对称地球模型不产生净电子自旋
Spherically symmetric Earth models yield no net electron spin
AI总结：
本文研究了地球电子自旋，发现球对称地球模型中电子自旋矢量和为零，基于地球球对称性破缺的最大三个因素估算出沿地球自转轴的净自旋极化电子下限，表明基于近日点进动提取的单极-偶极耦合界限需放宽约2000倍。
摘要：
利用地球中的电子作为自旋极化源的地面实验已被证明能够为奇异的长程自旋-自旋和自旋-速度相互作用提供强有力的限制。这些界限约束了许多被提出的超轻玻色子暗物质候选者的耦合强度。最近，有研究指出，太阳与地球自旋极化电子之间的单极-偶极耦合将导致地球近日点进动的改变。利用对地球净自旋极化的估计以及地球近日点进动的实验界限，人们对该单极-偶极耦合的量级施加了有趣的约束。在此，我们研究了与地球电子相关的自旋。我们发现，在地幔和地壳中约有 $6 \ imes 10^{41}$ 个自旋极化电子，其方向与局部磁场反平行。然而，当对任何球对称地球模型进行积分时，我们发现这些自旋的矢量和为零。为了确定沿地球自转轴的净自旋量级的下界，我们研究了地球球对称性被打破的三个最大因素：地幔的大型低剪切波速省、地壳成分以及地球的扁球体。从这些研究中我们得出结论，至少有 $5 \ imes 10^{38}$ 个自旋极化电子与地球自转轴反平行排列。这一分析表明，从地球近日点进动中提取的单极-偶极耦合界限需要放宽约 2000 倍。
英文摘要：
Terrestrial experiments that use electrons in Earth as a spin-polarized source have been demonstrated to provide strong bounds on exotic long-range spin-spin and spin-velocity interactions. These bounds constrain the coupling strength of many proposed ultralight bosonic dark-matter candidates. Recently, it was pointed out that a monopole-dipole coupling between the Sun and the spin-polarized electrons of Earth would result in a modification of the precession of the perihelion of Earth. Using an estimate for the net spin-polarization of Earth and experimental bounds on Earth's perihelion precession, interesting constraints were placed on the magnitude of this monopole-dipole coupling. Here we investigate the spin associated with Earth's electrons. We find that there are about $6 \times 10^{41}$ spin-polarized electrons in the mantle and crust of Earth oriented anti-parallel to their local magnetic field. However, when integrated over any spherically-symmetric Earth model, we find that the vector sum of these spins is zero. In order to establish a lower bound on the magnitude of the net spin along Earth's rotation axis we have investigated three of the largest breakdowns of Earth's spherical symmetry: the large low shear-velocity provinces of the mantle, the crustal composition, and the oblate spheroid of Earth. From these investigations we conclude that there are at least $5 \times 10^{38}$ spin-polarized electrons aligned anti-parallel to Earth's rotation axis. This analysis suggests that the bounds on the monopole-dipole coupling that were extracted from Earth's perihelion precession need to be relaxed by a factor of about 2000.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
