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From: Bacle on 7 Apr 2010 20:36 > This is a question from "Ask an Algebraic > Topologist" > > Hi, everyone: > > I am trying to find the homology of the following > simplicial complex K: > > A tetrahedral surface (i.e. a simplicial sphere) that > intersects > > 2 simple triangular curves (i.e., simplicial circles) > in a common vertex v , i.e., Let T be the tetrahedron > and T1,T2 be the triangles, > > and let /\ be intersection. then: > > T/\T1={v}= T/\T2 . > > **Problem **is that I don't know if I should treat > this as (the surface of ) a three-simplex , with > T1,T2 just 2-subsimplices of the surface, > > or if I should decompose it otherwise. > > Thanks. Correction: this is a 2-complex, not a 3-complex. and all its subsimplices. I am having trouble calculating the 2nd homology group, because I don't know how to calculate the incidence numbers; more specifically, the differential of a 2-chain: I have oriented the 3-simplex <vov1v2v3v4> How do I find the incidence number of the 3-simplex on the 2-simplices.?. Usually, given a 2-simplex <vov1v2>, and an incident 1-simplex , say ,<vov1>, we test if <v2vov1> is an even or odd permutation of <vov1v2>. *BUT* . How do we find the incidence number for the 2-simplex <vov1v2v3v4> with respect to its 1-subsimplices, say for <vov1>.?. Do we just check if <v2v3v4vov1> is an even/odd permutation of <vov1v2v3v4>.? Thanks. |