Braids, trees, and operads
摘要
The space of unordered configurations of distinct points in the plane is aspherical, with Artin's braid group as its fundamental group. Remarkably enough, the space of ordered configurations of distinct points on the real projective line, modulo projective equivalence, has a natural compactification (as a space of equivalence classes of trees) which is also (by a theorem of Davis, Januszkiewicz, and Scott) aspherical. The classical braid groups are ubiquitous in modern mathematics, with applications from the theory of operads to the study of the Galois group of the rationals. The fundamental groups of these new configuration spaces are not braid groups, but they have many similar formal properties.
引用
@article{arxiv.math/0109086,
title = {Braids, trees, and operads},
author = {Jack Morava},
journal= {arXiv preprint arXiv:math/0109086},
year = {2007}
}
备注
Notes from an expository talk at the Gdansk conference on algebraic topology, 5 June 2001]