PATTERN FORMATION AND SYMMETRY OF FIELDS IN ELECTROHYDRODYNAMICSS IN LIQUID CRYSTALS

液晶电化学场的图案形成和对称性

• 批准号: 08454107
• 负责人: KAI Shoichi
• 金额: $ 5.06万
• 依托单位: KYUHSU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08454107/
• 关键词: Electrohydrodynamics; Liquid Crystals; Homeotropic Alignment; Symmetry; Goldstone Mode; Soft-Mode Turbulence; Defect Chaos; Continuously Rotational Symmetry; ホメオトロピック; 対流; 時空カオス; ゴールドストーンモード; 間欠カオス

The electrohydrodynamic instability (EHD) in nematic liquid crystals is investgated using homeotropically aligned systems where the nematic director orients perpendicular to the electrodes. In homeotropically aligned EHD the system has a continuously rotational symmetry as well as a translational one. This symmetry leads to additional new Goldstone modes at onset of convections and dramatically changes the bifurcation properties as well as observed patterns. The obtained results in the present study are as follows.1) In the system with additional Goldstone modes due to continuous rotational symmetry, a direct transition from nonconvective states to spatiotemporal chaos is observed.2) The bifuration at onset occurs supercritically. The correlation time of macroscopic randam motions becomes longer inversely proportional to the deviation from the onset, that is, a critical slowing down phenomenon is observed. From this behavior the spatiotemporal chaos has been named the soft mode turbule … More nce (SMT) .3) The stability of additional Goldstone modes can be controlled by application of magnetic field since magnetic fields induce the prefered axis and suppress the generation of the Goldstone modes. Therefore under superimposing strong magnetic fields periodic patterns are observed.4) New type of zig-zag patterns are found out which are not predicted in currently available thcories.5) It is clarified from these findings that driving forccs which result in SMT are induced by non-parallel orientation between the director and the wavevector of covective rolls.6) Depending on the strength of magnetic fields there are two types of spatiotemporal chaos. The transition between them is clearly defined by looking the spatial power spectra of patterns and distribution functions of roll orientations.7) The rolls exist either in all directions or only in the prefered directions induced by magnetic fields. Then the formet one is called SMT and the latter the defect turbulence.Thus excess of symmetry can result in chaos and the intrinsic mechanism for direct transition to chaos from a spatially uniform state is destabilization of short-wavelength modes due to coupling with Goldstone modes of the spectrum. Based on these results, new theory will be expected in EHD. Less

使用垂直排列系统研究向列液晶中的电流体动力学不稳定性（EHD），其中向列指向矢垂直于电极取向。在垂直排列的 EHD 中，系统具有连续旋转对称和平移对称。这种对称性导致对流开始时产生额外的新戈德斯通模式，并显着改变分叉特性以及观察到的模式。本研究获得的结果如下：1）在由于连续旋转对称而具有附加戈德斯通模的系统中，观察到从非对流态到时空混沌的直接转变。2）开始时的分岔发生在超临界状态。宏观随机运动的相关时间变得更长，与起始点的偏差成反比，即观察到临界减速现象。从这种行为中，时空混沌被命名为软模式湍流 (SMT) .3) 附加戈德斯通模式的稳定性可以通过施加磁场来控制，因为磁场会诱导首选轴并抑制戈德斯通模式的生成。因此，在叠加的强磁场下，观察到周期性模式。4) 发现了目前可用理论中未预测到的新型锯齿形模式。5) 从这些发现中澄清，导致 SMT 的驱动力是由对流滚子的指向矢​​和波矢量之间的非平行方向引起的。6) 根据磁场的强度，存在两种类型的时空混沌。通过查看图案的空间功率谱和滚动方向的分布函数可以清楚地定义它们之间的过渡。7）滚动要么存在于所有方向上，要么仅存在于磁场感应的首选方向上。前一种称为SMT，后一种称为缺陷湍流。因此，过度对称会导致混沌，而从空间均匀状态直接过渡到混沌的内在机制是由于与光谱的戈德斯通模式耦合而导致短波长模式不稳定。基于这些结果，EHD 中将出现新的理论。较少的

项目成果

Yoshiki HIDAKA: "Formation and Dynamics of Convective Pattern in Homeotropic System of Nematic Liquid Crystals" Molecular Crystals and Liquid Crystals. 302. 385-390 (1997)

Yoshiki HIDAKA：“向列液晶垂直系统中对流模式的形成和动力学”分子晶体和液晶。

Yoshiki HIDAKA,Jong-Hoon HUH,Ken-ichi HAYASHI,Michael I.TRIBELSKY,Shoichi KAI: "Dynamical Aspects of Spatiotemporal Chaos at the Onset of Electroconvection in Homeotropic Nematics" J.Phys.Soc.Jpn.vol.66, no.11. 3329-32 (1997)

Yoshiki HIDAKA、Jong-Hoon HUH、Ken-ichi HAYASHI、Michael I.TRIBELSKY、Shoichi KAI：“垂直向列学中电对流开始时时空混沌的动态方面”J.Phys.Soc.Jpn.vol.66，no。

Yoshiki HIDAKA: "Dynamics of Eckhaus Modes in One-Dimensional Electroconvection Patterns in Nematics" Molecular Crystals and Liquid Crystals. 302. 357-362 (1997)

Yoshiki HIDAKA：“向列学中一维电对流模式的埃克豪斯模式动力学”分子晶体和液晶。

Shoichi KAI: "Physics of Dissipative Structures in Liquid Crystals (in Japanese)" Polymer (Kohbunnshi). vol.46, no.9. 681-1 (1997)

Shoichi KAI：“液晶耗散结构物理学（日语）”聚合物（Kohbunnshi）。

S.Kai: "Universal Defect Dynamics in Two Dimensional Convective Roll Patterns" J.Physical Society of Japan. 65-11. 3419-3422 (1996)

S.Kai：“二维对流滚动模式中的通用缺陷动力学”J.日本物理学会。