We examine the dynamics of a compressible active nematic liquid crystal on a frictional substrate. When frictional damping dominates over viscous dissipation, we eliminate flow in favor of active stresses to obtain a minimal dynamical model for the nematic order parameter, with elastic constants renormalized by activity. The renormalized elastic constants can become negative at large activity, leading to the selection of spatially inhomogeneous patterns via a mechanism analogous to that responsible for modulated phases arising at an equilibrium Lifshitz point. Tuning activity and the degree of nematic order in the passive system, we obtain a linear stability phase diagram that exhibits a nonequilibrium tricritical point where ordered, modulated and disordered phases meet. Numerical solution of the nonlinear equations yields a succession of spatial structures of increasing complexity with increasing activity, including kink walls and active turbulence, as observed in experiments on microtubule bundles confined at an oil-water interface. Our work provides a minimal model for an overdamped active nematic that reproduces all the nonequilibrium structures seen in simulations of the full active nematic hydrodynamics and provides a framework for understanding some of the mechanisms for selection of the nonequilibrium patterns in the language of equilibrium critical phenomena.
Elasticity-Driven Periodic Polarization Patterns in Confined Chiral Ferroelectric Nematic Fluid
Jožef Stefan Institute（约瑟夫·斯特凡研究所）；Faculty of Mathematics and Physics, University of Ljubljana（卢布尔雅那大学数学与物理学院）；CENN Nanocenter（CENN纳米中心）；Department of Physics, Faculty of Science and Technology, University of the Basque Country UPV/EHU（巴斯克国立大学理学院物理系）；School of Chemistry, University of Leeds（利兹大学化学学院）；School of Physics and Astronomy, University of Leeds（利兹大学物理与天文学院）
Note: Formation of the nematic splay-bend in two-dimensional systems of bow-shaped particles
最近，Tavarone等人（J.Chem.Phys.143，114505（2015））讨论了由三根针组成的锯齿形和弓形颗粒的相行为。作者提出了非常有趣的结果，广泛的蒙特卡罗模拟与周期性的边界条件，在恒定的NVT和恒定的NPT合奏。除了各向同性、非晶相和近晶相之外，他们还确定了一种调制的非晶相，这实际上是非晶核系统长期预期的展曲-弯曲相（$N_{SB}$）（Europhys. Lett. 56，247（2001））。他们还用平均场近似下的密度泛函理论描述了各向同性-向列相和向列相-近晶相的转变。但是，作者没有提供$N_{SB}$的理论描述。在这里，我们提出了一个简单的理论相变的$N_{SB}$阶段，以填补空白。在我们的研究中，我们使用Onsager型密度泛函理论与完美的顺序近似和调制结构的Meyer参数化。我们提出的结果为任意比例的中心和侧段的长度和开口角度的弓形颗粒。
Double Splay Nematic Order in Confined Polar Fluids
Southern University of Science and Technology（南方科技大学）；The Hongkong University of Science and Technology（香港科技大学）；South China Advanced Institute for Soft Matter Science and Technology (AISMST), School of Emergent Soft Matter, South China University of Technology（华南理工大学 emergent soft matter 学院 / 华南软物质科学与技术先进研究院）；Guangdong Provincial Key Laboratory of Functional and Intelligent Hybrid Materials and Devices, South China University of Technology（华南理工大学 广东省功能与智能杂化材料器件重点实验室）
Splay and polar order in a system of hard pear-like molecules: confrontation of Monte Carlo numerical simulations with density functional theory calculations
Modulated Anti-Ferroelectric Smectic Phases with Orthogonal and Tilted Structures
School of Physics & Astronomy, University of Leeds（利兹大学物理与天文学院）；School of Chemistry, University of Leeds（利兹大学化学学院）；Complex Matter Department, Jožef Stefan Institute（约瑟夫·斯蒂芬研究所复杂物质部）；Faculty of Mathematics and Physics, University of Ljubljana（卢布尔雅那大学数学与物理学院）
