Topological defects at the boundary of neutron 3P2 superfluids in neutron stars
Topological defects at the boundary of neutron 3P2 superfluids in neutron stars
复制标题
中子星中子3P2超流体边界的拓扑缺陷
DOI：
10.1103/physrevc.101.025204
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发表时间：
2020
影响因子：
3.1
通讯作者：
Nitta Muneto
中科院分区：
文献类型：
--
作者：
Yasui Shigehiro;Chatterjee Chandrasekhar;Nitta Muneto
我们研究了中子星中中子超流体的表面效应。超流体根据磁场强度由小到大，分别处于单轴向列相（UN）、双轴向列相（BN）或BN相。我们假设一个中子超流体在一个有球面边界的球里。采用合适的冷凝物边界条件，求解了金兹堡-朗道方程，得到了中子超流体的几种表面性质。首先，表面上的相位可能与体相不同，表面上通常会发生对称性恢复或断裂。其次，表面能量密度的分布随球体的极角而具有各向异性，这可能导致表面几何形状的变形。第三，冷凝物在表面上诱导的二维矢量场所描述的有序参数流形允许在表面上存在拓扑缺陷（涡），并且由于poincar<s:1> - hopf定理，即使在基态也必须存在这样的缺陷：尽管涡和反涡的数量取决于体相，但它们之间的差异在拓扑上是不变的（欧拉数），与体相无关。这些漩涡不会延伸到整体，在液晶和氦-3超流体的背景下被称为boojums。本文所发现的中子超流体的表面性质可以为我们研究中子星提供有用的信息。
We study surface effects of neutronsuperfluids in neutron stars.superfluids are in uniaxial nematic (UN),biaxial nematic (BN), orBN phase, depending on the strength of magnetic fields from small to large. We suppose a neutronsuperfluid in a ball with a spherical boundary. Adopting a suitable boundary condition forcondensates, we solve the Ginzburg-Landau equation to find several surface properties for the neutronsuperfluid. First, the phase on the surface can be different from that of the bulk, and symmetry restoration or breaking occurs in general on the surface. Second, the distribution of the surface energy density has an anisotropy depending on the polar angle in the sphere, which may lead to the deformation of the geometrical shape of the surface. Third, the order parameter manifold induced on the surface, which is described by two-dimensional vector fields induced on the surface from the condensates, allows topological defects (vortices) on the surface, and there must exist such defects even in the ground state thanks to the Poincaré-Hopf theorem: although the numbers of the vortices and antivortices depend on the bulk phases, the difference between them is topologically invariant (the Euler number) irrespective of the bulk phases. These vortices, which are not extended to the bulk, are called boojums in the context of liquid crystals and helium-3 superfluids. The surface properties of the neutronsuperfluid found in this paper may provide us useful information to study neutron stars.