All Questions
8 questions
11
votes
1
answer
683
views
Fixed-point-free group action on a finite, contractible, 3-dimensional simplicial complex
Let $K$ be a finite simplicial complex with an admissible action of a finite group $G$.
(Terminology: By an action of a group $G$ on $K$ I mean an action by simplicial automorphisms. The action is ...
- 2,104
6
votes
1
answer
479
views
Abstract simplicial complexes - Reference for an elementary definition of mapping degree for simplicial maps?
I am interested to use the mapping degree for simplicial maps between (oriented) abstract simplicial complexes. What I mean by "elementary": My preference would be to use a definition of ...
- 6,917
6
votes
1
answer
530
views
References to proofs of a theorem by Van Kampen-Flores
Theorem (Van Kampen-Flores 1930s) From any 7 points in four-dimensional space one can choose two disjoint triples such that the triangles with vertices at the triples intersect each other.
This ...
6
votes
0
answers
132
views
Is there any work in topological data analysis on something like "Voronoi complexes"?
Given a finite set $X \subset \mathbb{R}^n$, we can of course construct the corresponding Čech or Vietoris-Rips filtration. At each level of this filtration the scale parameter is fixed and unrelated ...
- 15.4k
4
votes
1
answer
362
views
Who first considered constructibility of simplicial complexes?
A simplicial complex of dimension $d$ is called constructible if it is a simplex, or if it is the union of two constructible dimension-$d$ simplicial complexes along a dimension-$(d-1)$ intersection. ...
- 1,500
4
votes
1
answer
169
views
"Almost embedding" the complete 2-dimensional complex $\mathcal K_7^2$ into $\Bbb R^4$
Let $\mathcal K_7^2$ be the complete 2-dimensional simplicial complex on seven vertices, i.e. it has all $7\choose 2$ edges and all $7\choose 3$ 2-simplices (and no higher-dimensional simplices).
I ...
- 13.6k
4
votes
0
answers
183
views
In how far does the Whitney trick work in the piecewise linear setting in $\Bbb R^4$?
I usually read about the Whitney trick in the context of smooth manifolds, but I wonder in how far it works in the piecewise linear (PL) category as well. I have a specific setting in mind that I will ...
- 13.6k
3
votes
0
answers
88
views
Is the thickening of a PL 2-disc in $\Bbb R^4$ a 4-ball?
Let $D\subset\Bbb R^4$ be a PL-embedded 2-dimensional disc. Let $N=D+K$ be a thickening of the disc, where $K$ is some sufficiently small 4-dimensional PL-ball and "$+$" means Minkowski ...
- 13.6k