pith. sign in

arxiv: 1210.7361 · v2 · pith:NFOU3JT6new · submitted 2012-10-27 · 🧮 math.GT

How do curved spheres intersect in 3-space?

classification 🧮 math.GT
keywords circlesdisjointspherespheresunionalgorithmconditionexist
0
0 comments X
read the original abstract

The following problem was proposed in 2010 by S. Lando. Let $M$ and $N$ 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 $M$ in one sphere and as $N$ in the other? Union $M'$ of disjoint circles is {\it situated} in one sphere as union $M$ of disjoint circles in the other sphere if there is a homeomorphism between these two spheres which maps $M'$ to $M$. We prove (by giving an explicit example) that the answer to this problem is "no". We also prove a necessary and sufficient condition on $M$ and $N$ 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 $M$ and $N$. It is an open question if a faster algorithm exist.

This paper has not been read by Pith yet.

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.