English

Simple connectedness of the Ran space

Algebraic Topology 2026-02-20 v3 General Topology

Abstract

The space of all finite non-empty subsets of a topological space XX, also known as the Ran space of XX, is weakly contractible for XX path connected. We consider subspaces Rann(X)\mathrm{Ran}_{\leqslant n}(X) of the Ran space given by all subsets of XX of size at most nn, and present results on their first homotopy groups. In particular, we show that the induced map π1(Rann(X))π1(Rann+2(X))\pi_1(\mathrm{Ran}_{\leqslant n}(X)) \to \pi_1(\mathrm{Ran}_{\leqslant n+2}(X)) is trivial for all positive integers nn, and even more, show that π1(Rann(X))=0\pi_1(\mathrm{Ran}_{\leqslant n}(X)) = 0 for all n4n\geqslant 4, by explicitly drawing the path homotopies that contract any loop to a point.

Keywords

Cite

@article{arxiv.2602.09815,
  title  = {Simple connectedness of the Ran space},
  author = {Jānis Lazovskis},
  journal= {arXiv preprint arXiv:2602.09815},
  year   = {2026}
}

Comments

Key related work added. 6 pages, 3 figures. Comments welcome

R2 v1 2026-07-01T10:29:47.119Z