标题： 格点上的矢量活性物质：极性凝聚态和向列丝状物 显示英文标题

标题： Vectorial active matter on the lattice: polar condensates and nematic filaments

摘要： 我们引入了一种新颖的格子气体细胞自动机（LGCA），用于可压缩的矢量活性物质，具有极性和向列速度对齐。 相互作用在构造上是零范围的。 对于极性对齐，我们表明系统经历了一个相变，促进了聚集，与经典的零范围过程有很强的相似性。 我们发现，在临界点以上，系统中宏观比例的粒子状态凝聚到同一状态，共享相同的位置和动量（极性凝聚态）。 对于向列对齐，系统也表现出凝聚现象，但存在根本差异：系统中宏观比例的粒子坍缩成一个纤维，其中粒子仅有两种可能的动量。 此外，我们推导了活性LGCA模型的流体动力学方程，以理解系统经历的相变和凝聚现象。 我们还表明，一般来说，离散的格子对称性——例如正方形或六边形晶格的对称性——极大地影响了格子上活性系统的涌现大尺度特性。 这项研究表明，在格子上对齐的活性物质表现出新的行为，包括向与凝聚模型相似的状态的相变。 显示英文摘要

摘要： We introduce a novel lattice-gas cellular automaton (LGCA) for compressible vectorial active matter with polar and nematic velocity alignment. Interactions are, by construction, zero-range. For polar alignment, we show the system undergoes a phase transition that promotes aggregation with strong resemblance to the classic zero-range process. We find that above a critical point, the states of a macroscopic fraction of the particles in the system coalesce into the same state, sharing the same position and momentum (polar condensate). For nematic alignment, the system also exhibits condensation, but there exist fundamental differences: a macroscopic fraction of the particles in the system collapses into a filament, where particles possess only two possible momenta. Furthermore, we derive hydrodynamic equations for the active LGCA model to understand the phase transitions and condensation that undergoes the system. We also show that generically the discrete lattice symmetries -- e.g. of a square or hexagonal lattice -- affect drastically the emergent large-scale properties of on-lattice active systems. The study puts in evidence that aligning active matter on the lattice displays new behavior, including phase transitions to states that share similarities to condensation models.