城市秩序的几何结构
Geometry of Urban Order
- Université Paris-Saclay（巴黎萨克雷大学）
- CNRS（法国国家科学研究中心）
- CEA（法国原子能和替代能源委员会）
- Institut de Physique Théorique（理论物理研究所）
- Centre d’Analyse et de Mathématique Sociales（社会分析与数学中心）
- EHESS（高等社会科学学院）
- Complexity Science Hub（复杂性科学中心）
- University of Southern California（南加州大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究通过引入方位社区概念，分析全球1025个城市的街道网络，发现城市由高度有序的晶粒组成，其全局秩序主要由晶粒数量决定，并提出了基于界面分数的城市形态分类图。
AI中文摘要：
城市街道网络被建模为空间图，其几何结构反映了规划、历史和物理约束。全局方向度量描述了城市的整体秩序，但并未揭示街道方向如何形成连贯的街区。在此，我们引入“方位社区”——共享共同方向的街道所组成的空间连通区域——并利用多晶材料物理学中的概念对其进行分析。在全球1025个大城市中，这些区域几乎完美有序：其平均相干性为0.964，且在不同城市间仅变化1.4%，远高于随机方向街道的预期值。因此，每个城市都是有序取向晶粒的马赛克，仅在数量、大小和相互排列上有所不同。由于晶粒在各处同样规则，城市的全局秩序主要取决于其平均覆盖的晶粒数量：城市显得有序是因为它由少数大晶粒构成，而非因其结构在局部更为规则。一个将晶粒方向随机化的零模型证实了这一晶粒计数机制。最后，界面分数γ衡量区域间的互锁程度，产生了一个形态图，将城市连续地组织在网格状、多晶和碎片化极限之间。
英文摘要：
Urban street networks are modeled as spatial graphs whose geometry reflects planning, history, and physical constraints. Global orientation measures describe the overall order of a city but do not reveal how street directions form coherent neighborhoods. Here we introduce bearings communities---spatially connected domains whose streets share a common orientation---and analyze them using concepts from the physics of polycrystalline materials. Across $1025$ large cities worldwide, these domains are almost perfectly ordered: their mean coherence is $0.964$ and varies by only $1.4\%$ from one city to the next, far above the value expected for randomly oriented streets. Every city is therefore a mosaic of well-ordered orientational grains, differing only in their number, size, and mutual alignment. Because the grains are equally regular everywhere, a city's global order is set mainly by how many of them it averages over: a city appears ordered because it is built from a few large grains, not because its fabric is locally more regular. A null model in which grain orientations are randomized confirms this grain-counting mechanism. Finally, the interface fraction $γ$ measures how strongly domains interlock, yielding a morphology diagram that organizes cities continuously between grid-like, polycrystalline, and fragmented limits.
