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Results tagged with crossed-modules
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user 13767
13
votes
2
answers
727
views
Given a Kirby diagram of a 4-manifold, what's its homotopy 2-type?
It's easy to derive a presentation of the fundamental group of a 4-manifold if you have a Kirby diagram: The 1-handles are generators and the 2-handles are the relations. The 3- and 4-handles, which a …
- 5,565
8
votes
1
answer
184
views
Can I recover a crossed module by its homomorphisms?
This is a follow up to this question.
Imagine there is a finitely presented crossed module $\mathcal{G} = (G,H, -\triangleright-\colon G \to \operatorname{Aut}(H), \delta\colon H \to G)$ which I do …
- 5,565