English

How do curved spheres intersect in 3-space?

Geometric Topology 2014-11-27 v2

Abstract

The following problem was proposed in 2010 by S. Lando. Let MM and NN be two unions of the same number of disjoint circles in a sphere. Do there always exist two spheres in 3-space such that their intersection is transversal and is a union of disjoint circles that is situated as MM in one sphere and as NN in the other? Union MM' of disjoint circles is {\it situated} in one sphere as union MM of disjoint circles in the other sphere if there is a homeomorphism between these two spheres which maps MM' to MM. We prove (by giving an explicit example) that the answer to this problem is "no". We also prove a necessary and sufficient condition on MM and NN for existing of such intersecting spheres. This result can be restated in terms of graphs. Such restatement allows for a trivial brute-force algorithm checking the condition for any given MM and NN. It is an open question if a faster algorithm exist.

Keywords

Cite

@article{arxiv.1210.7361,
  title  = {How do curved spheres intersect in 3-space?},
  author = {Sergey Avvakumov},
  journal= {arXiv preprint arXiv:1210.7361},
  year   = {2014}
}

Comments

9 pages, 9 figures

R2 v1 2026-06-21T22:28:43.049Z