English

Homotopy Groups of Diagonal Complements

Algebraic Topology 2016-11-16 v2

Abstract

For XX a connected finite simplicial complex we consider Δd(X,n)\Delta^d(X,n) the space of configurations of nn ordered points of XX such that no d+1d+1 of them are equal, and Bd(X,n)B^d(X,n) the analogous space of configurations of unordered points. These reduce to the standard configuration spaces of distinct points when d=1d=1. We describe the homotopy groups of Δd(X,n)\Delta^d(X,n) (resp. Bd(X,n)B^d(X,n)) in terms of the homotopy (resp. homology) groups of XX through a range which is generally sharp. It is noteworthy that the fundamental group of the configuration space Bd(X,n)B^d(X,n) abelianizes as soon as we allow points to collide (i.e. d2d\geq 2).

Keywords

Cite

@article{arxiv.1306.6272,
  title  = {Homotopy Groups of Diagonal Complements},
  author = {Sadok Kallel and Ines Saihi},
  journal= {arXiv preprint arXiv:1306.6272},
  year   = {2016}
}

Comments

Major improvement from v1. A more careful use of Smale's result 6.1 has led to a new section 5. The main improvement is in the bound for Theorem 1.2 which is now sharp. This paper is to appear in AGT. 20 Pages

R2 v1 2026-06-22T00:40:45.730Z