5
votes
0answers
59 views
In cell-decomposed manifolds, how easy is it to arrange for the tubular neighborhood of a diagonal to contract onto the diagonal?
Suppose that you have decomposed a manifold $M$ into cells (I care most, if it matters, about compact oriented smooth manifolds; but if my question can be solved in the PL category …
16
votes
4answers
531 views
Is the space of diffeomorphisms homotopy equivalent to a CW-complex?
Clarification: My question concerns the homotopy type of the space of $C^k$ diffeomorphisms with the compact-open $C^k$ topology, where $0< k \leq\infty$. I have stated my quest …
3
votes
3answers
255 views
Conditions for a graph to be the 1- skeleton of a Surface
Given a connected finite graph G with degree at least 2 at each vertex, what are the conditions G needs to assume in order to attach 2-cells so that the CW- complex is a closed c …
0
votes
0answers
63 views
A sufficient condition for attaching squares to a 1 skeleton so that the CW-complex is a 2 - manifold
Suppose we have a finite connected graph $G$, I want to add 2 -cells to $G$ so that the 2 cells have boundaries of length 4 (squares) and so that $G$ is the 1 skeleton of a surfac …
7
votes
1answer
199 views
A description of cellular boundary maps in terms of a Morse function
I'm writing a paper on classical Morse Theory and I'm interested in applying Morse functions to the computation of homology groups of a compact manifold $M$. The standard way in wh …
17
votes
0answers
524 views
Manifolds admitting CW-structure with single n-cell
Let $M$ be a topological $n$-manifold, closed and connected (not necessarily oriented):
When does $M$ not admit (up to homotopy-type) a CW-structure with a single $n$-cell?
By cla …
1
vote
2answers
207 views
Second homotopy groups of 3-complexes and Fenn’s spiders.
Let $X$ be a finite CW complex then with one zero cell. Then (up to homotopy) the two skeleton of X is the same as a group presentation, via the Cayley complex construction. For a …
8
votes
3answers
441 views
Constructing a simplicial set homology-equivalent to a given CW complex
I would like to compute the homology of certain low dimensional CW complexes and I am hoping to take advantage of software that handles simplicial sets as input. Thus, I would like …
24
votes
6answers
2k views
What does actually being a CW-complex provide in algebraic topology?
From time to time, I pretend to be an algebraic topologist. But I'm not really hard-core and some of the deeper mysteries of the subject are still ... mysterious. One that came u …
3
votes
2answers
587 views
The definition of a CW complex and related notions
In the appendix of Allen Hatcher's book "Algebraic Topology", a CW complex is defined to be a space iteratively constructed by attaching $n$-cells onto an $(n-1)$ skeleton. There …
13
votes
1answer
684 views
Is a finite CW complex minus a point still homotopy equivalent to a finite CW complex?
Let $X$ be a finite CW complex and $x_0$ a point in $X$.
My question is then just:
Is $X-{x_0}$ still homotopy equivalent to a finite CW complex?
17
votes
1answer
663 views
Can the Alexander horned sphere arise as a cell boundary in a finite CW-sphere?
Recently, I've been wondering to what extent certain types of pathologies can arise in finite CW complexes -- notice that I do not want to assume that I'm in the PL category or tha …
6
votes
1answer
176 views
State of knowledge on the Commutative W-spaces which appear in “Model Categories of Diagram Spectra”
This is a follow-up question to another question I asked last month. In MMSS's "Model Categories of Diagram Spectra," the authors consider many different models for spectra and pro …
15
votes
3answers
905 views
The second homotopy group of a simple CW-complex
Let $X$ be a CW-complex with
one 0-cell
two 1-cells
three 2-cells
no cells in dimensions 3 or higher.
Is it always true that $\pi_2(X)\ne 1$?
15
votes
2answers
547 views
Does the following condition imply the homotopy type of a wedge of spheres?
Let me preface this question by saying that I am not an algebraic topologist.
Motivation. I was looking with a colleague at the homotopy type of a family of posets and we were abl …

