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4 votes
1 answer
181 views

What is a sufficient set of links in a simplicial complex to represent any PL manifold?

The link of a vertex in a $n$-dimensional simplicial complex is the $(n-1)$-dimensional simplicial complex formed by the $(n-1)$-simplices each of which, together with the vertex, spans an $n$-simplex …
Andi Bauer's user avatar
  • 2,839
2 votes
Accepted

Are there invariants of cell complexes similar to the Euler characteristic?

As pointed out in the comments, every characteristic class in $H^d(BO(d), G)$ provides a $G$-valued locally computable invariant of $d$-manifolds, by pulling back via the classifying map of the tangen …
Andi Bauer's user avatar
  • 2,839
2 votes

Are there invariants of cell complexes similar to the Euler characteristic?

Meanwhile it seems to me that the discrete analogues to all Stiefel-Whitney numbers of $d$-dimensional manifolds are invariants of this type: First, for every $n$ there is a rule to color every $d-n$ …
Andi Bauer's user avatar
  • 2,839
9 votes
3 answers
368 views

Are there invariants of cell complexes similar to the Euler characteristic?

The Euler characteristic is an invariant (under homeomorphism) of manifolds that can be computed from a cellulation by (weighted) counting of different kinds of objects, namely \begin{equation} \chi=\ …
Andi Bauer's user avatar
  • 2,839
12 votes
3 answers
561 views

Is there a discrete lattice analogue of conformal transformations?

There is a simple discrete combinatorial analogue of manifolds and homeomorphisms: Replace manifolds by simplicial complexes and homeomorphisms by Pachner moves. Equivalence classes of manifolds under …
Andi Bauer's user avatar
  • 2,839
8 votes
0 answers
158 views

Is there a combinatorial representation of general topological manifolds similar to triangul...

Piece-wise linear manifolds are combinatorially represented by simplicial complexes modulo Pachner moves. However, for dimensions greater than $3$, the notions of piece-wise linear and topological man …
Andi Bauer's user avatar
  • 2,839
3 votes
0 answers
118 views

Which Stiefel-Whitney numbers can be extended to manifolds with boundaries?

The Stiefel-Whitney numbers are classical topological manifold invariants obtained by integrating some local quantity (a cup product of Stiefel-Whitney classes) over the manifold. Which Stiefel-Whitne …
Andi Bauer's user avatar
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