Title: Vortex formation and dynamics of defects in shells of active nematics Show Chinese title

Title: 活性向列壳中的涡旋形成和缺陷动力学

Abstract: We present a hydrodynamic model for a thin spherical shell of active nematic liquid crystal with an arbitrary configuration of defects. The active flows generated by defects in the director lead to the formation of stable vortices, analogous to those seen in confined systems in flat geometries, which generate an effective dynamics for four +1/2 defects that reproduces the tetrahedral to planar oscillations observed in experiments. As the activity is increased and the vortices become stronger, the defects are drawn more tightly into pairs, rotating about antipodal points. We extend this situation to also describe the dynamics of other configurations of defects. For example, two +1 defects are found to attract or repel according to the local geometric character of the director field around them, while additional pairs of opposite charge defects can give rise to flow states containing more than two vortices. Finally, we describe the generic relationship between defects in the orientation and singular points of the flow, and suggest implications for the three-dimensional nature of the flow and deformation in the shape of the shell. Show Chinese abstract

Abstract: 我们提出了一种用于具有任意缺陷配置的活性向列液晶薄球壳的流体力学模型。 由指向矢中的缺陷产生的活性流动导致稳定涡旋的形成，类似于在平坦几何中受限系统中观察到的涡旋，这些涡旋为四个+1/2缺陷提供了有效动力学，重现了实验中观察到的四面体到平面振荡。 随着活性增加，涡旋变得更加强烈，缺陷被更紧密地吸引成对，并围绕对跖点旋转。 我们将这种情况扩展以描述其他缺陷配置的动力学。 例如，两个+1缺陷根据它们周围指向矢场的局部几何特性而相互吸引或排斥，而额外的相反电荷缺陷对可能会产生包含多个涡旋的流动状态。 最后，我们描述了取向缺陷与流动奇点之间的普遍关系，并提出了对壳层流动和形变三维性质的含义。