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awarded  Revival
1d
revised Properties of nerve of strict n-groupoid
added another reference
1d
revised Properties of nerve of strict n-groupoid
typo
1d
comment 2-groups are to crossed modules as 2-categories are to…?
I agree with the answer that crossed modules require the invertibility. However broadening rather than narrowing does work! That is going from globular or simplicial to cubical; see the paper Al-Agl/Brown/Steiner `Multiple categories: the equivalence between a globular and cubical approach', Advances in Mathematics, 170 (2002) 71-118.
1d
revised How to construct a free 2-group on a groupoid?
typo
2d
revised Properties of nerve of strict n-groupoid
typos
2d
answered How to construct a free 2-group on a groupoid?
2d
answered Properties of nerve of strict n-groupoid
2d
comment Cubical vs. simplicial singular homology
Re using polyhedra: the 1984 Bangor thesis of David Jones on "Poly T-complexes" is available from pages.bangor.ac.uk/~mas010/doctorates.html though that is concerned with defining "compositions" of polyhedral objects, i.e. homotopy rather than homology. The notion of "marked complex" defined there turns out to be equivalent to that of discrete Morse theory on regular cell complexes!
Jan
29
comment Undergraduate Topology
@The Mathemagician Many thanks for the comment! One person has called my exposition "idiosyncratic". I suppose that means I never assume an account of topology, or mathematics, is a kind of sacred text - "paths" have to be of length 1, "topologies" are defined in terms of open sets, "groups" are the fundamental idea, ...An exegesis shows one has to consider how the ideas arose. see pages.bangor.ac.uk/~mas010/einst.html, and also try to make the abstract ideas "concrete". See also my Galway exposition on my preprint page, for "anomalies in algebraic topology". I keep trying!
Jan
28
awarded  Enlightened
Jan
28
awarded  Nice Answer
Jan
25
revised The fundamental groupoid and a pushout in the category of groupoids.
added 152 characters in body
Jan
23
revised Crossed module structure on homotopy groups.
added more intuition
Jan
22
awarded  Necromancer
Jan
22
revised strict 2-groups VS crossed modules
added a comment on Mac Lane's book
Jan
22
revised Crossed module structure on homotopy groups.
added extra info and links
Jan
22
awarded  Necromancer
Jan
21
answered strict 2-groups VS crossed modules
Jan
21
revised Grothendieck's Homotopy Hypothesis - Applications and Generalizations
added some extra points