Topological defects (TDs) appear in all branches of physics due to the simplicity of generic mechanisms: The necessary condition for their existence is spontaneous symmetry breaking in a relevant physical field. Nematic liquid crystals (NLCs) represent an ideal testbed for their study and they can display point, line, textures, and in favorable conditions also wall defects. TDs in NLCs can be relatively easily created, controlled, and experimentally observed. This enables a detailed and controlled analysis of their physical properties, leading to the cross-fertilization of knowledge among different areas of physics, including condensed matter, particle physics, and cosmology. Furthermore, TDs in NLCs could be exploited in diverse applications. Herein, some salient features of most common TDs in NLCs, their generic mechanisms, their importance for fundamental science, and possible applications based on them are illustrated.

中文翻译：

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向列液晶的拓扑缺陷：基础物理实验室

由于通用机制的简单性，拓扑缺陷 (TD) 出现在物理学的所有分支中：它们存在的必要条件是相关物理领域中的自发对称性破缺。向列液晶 (NLC) 是他们研究的理想测试平台，它们可以显示点、线、纹理，在有利条件下还可以显示壁缺陷。NLC 中的 TD 可以相对容易地创建、控制和实验观察。这使得能够对其物理特性进行详细和受控的分析，从而导致不同物理领域（包括凝聚态物理、粒子物理和宇宙学）之间的知识交叉融合。此外，NLC 中的 TDs 可以在不同的应用中使用。在此，NLC 中最常见 TD 的一些显着特征、它们的通用机制、