Making the world from topological order

• 来源期刊: 国家科学评论（英文版）
• 年，卷（期）: 2019,（2）
• 页码范围: 227-230
• 页数: 4页
• 语种: 英文
• DOI: 10.1093/nsr/nwy116

摘要

Topology used to be a term confined to a branch of pure mathematics, where it referred to an invariant property of shape.The classic example was the way objects containing a single hole, like a torus and a coffee cup with handle, can be smoothly moulded into one another without tearing.But topological considerations have long played a role in the physics of matter, where for example they might dictate particular arrangements of component parts that can't be erased from the system.The classic example here is the fact that a'hairy ball'can't be combed flat without having at least two pointy tufts.Such'defects' in organization can be considered'topologically protected;since they are robust against any recombing of the hair.They are universal features that don't depend on the material specifics of the system:topological defects in liquid crystals are analogous to defects in spacetime called cosmic strings.