We numerically study the orientation deformations in nematic liquid crystals around charged particles. We set up a Ginzburg-Landau theory with inhomogeneous electric field. If the dielectric anisotropy varepsilon_1 is positive, Saturn ring defects are formed around the particles. For varepsilon_1<0, novel "ansa" defects appear, which are disclination lines with their ends on the particle surface. We find unique defect structures around two charged particles. To lower the free energy, oppositely charged particle pairs tend to be aligned in the parallel direction for varepsilon_1>0 and in the perpendicular plane for varepsilon_1<0 with respect to the background director . For identically charged pairs the preferred directions for varepsilon_1>0 and varepsilon_1<0 are exchanged. We also examie competition between the charge-induced anchoring and the short-range anchoring. If the short-range anchoring is sufficiently strong, it can be effective in the vicinity of the surface, while the director orientation is governed by the long-range electrostatic interaction far from the surface.
Topological defects and the short-distance behavior of the structure factor in nematic liquid crystals
从理论上研究了含有拓扑缺陷的双折射系统中波矢幅值k较大的光的光的散射。在大k时，结构因子S（k）主要由幂律贡献所支配，幂律贡献来自与拓扑缺陷相关的奇异序参数变化和指向矢的横向热涨落。这些缺陷（双向错和刺猬）导致形式为rho A k^{-xi}（"Porod尾“）的贡献，其中rho是给定类型缺陷的数密度，A是无量纲Porod振幅，xi是整数值Porod指数。的Porod振幅和指数计算的所有类型的拓扑稳定的缺陷发生在单轴和双轴向列在两个或三个空间维度。的范围内的波矢量的散射强度的贡献，由于缺陷占主导地位的贡献，由于热波动的估计，它的结论是，对于实验上可访问的缺陷密度的范围内的可观测性的Porod尾部扩展超过一个到三十年的散射波矢量的大小k。分析了现有的单轴向列相序实验结果，并提出了我们的研究结果的应用程序的光散射研究的其他系统包含大量的缺陷。
Irreversibility and symmetry breaking in the creation and annihilation of defects in active living matter
Zuckerberg Institute for Water Research, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev（本-古里安大学）；The Department of Physics, Ben-Gurion University of the Negev（本-古里安大学）；The Swiss Institute for Dryland Environmental and Energy Research, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev（本-古里安大学）；Department of Theoretical Physics, University of Geneva（日内瓦大学）；Department of Mathematics, Bar-Ilan University（巴伊兰大学）
