2020-01-14 08:34:00 +0200 received badge ● Taxonomist 2018-05-21 22:37:25 +0200 received badge ● Notable Question (source) 2018-05-21 22:37:25 +0200 received badge ● Popular Question (source) 2012-07-20 06:07:44 +0200 received badge ● Supporter (source) 2012-07-19 07:33:41 +0200 commented question Homology of chain complexes Considerng the boundary maps: it's d0:ZZ^3->0 d1:ZZ^4->ZZ^3 d2:ZZ^2->ZZ^4 (and d3:0->ZZ^2, which I omitted) Considering the worksheet: I edited it in the main question 2012-07-19 07:33:00 +0200 answered a question Homology of chain complexes Considerng the boundary maps: it's d0:ZZ^3->0 d1:ZZ^4->ZZ^3 d2:ZZ^2->ZZ^4 (and d3:0->ZZ^2, which I omitted) Considering the worksheet: It says: Worksheet is publicly viewable at http://www.sagenb.org/home/pub/4890 - however, I can't access it via the link either. Don't know if there's any way to fix it. Gonna edit it in the main question 2012-07-18 09:31:31 +0200 received badge ● Editor (source) 2012-07-18 09:30:25 +0200 asked a question Homology of chain complexes I've got the following chain complex: 0->ZZ^2->ZZ^4->ZZ^3->0 With the boundarymaps given by d0:(z1,z2,z3) |-> 0 d1:(z1,z2,z3,z4) |-> (-2(z1+z3+z4), 2(z1-z2), z2+z3+z4) d2:(z1,z2)|-> (z1+z2, z1+z2,-z1,-z2) Now I tried to compute the homology groups (e.g. H0 = ker d0 / im d1) using sage. One time manually via taking the quotients of the respective modules, one time using the ChainComplex() module. However, I don't really understand the output using the first method (e.g. what means: "Finitely generated module V/W over Integer Ring with invariants (2, 0)"), and both methods seem to deliver different results... I've defined my boundary maps as matrices: d0 = matrix(ZZ, 1,3,[[0,0,0]]).transpose() d1 = matrix(ZZ, 3,4,[[-2,0,-2,-2],[2,-2,0,0],[0,1,1,1]]).transpose() d2 = matrix(ZZ,4,2,[[1,1],[1,1],[-1,0],[0,-1]]).transpose()  Where I've taken the transpose since I'm used to write linear maps as d(x) = Dx, whereas sage seems to use d(x) = xD, where D is the corresponding matrix. Calculating the homology groups via H0 = d0.kernel()/d1.image() H1 = d1.kernel()/d2.image() H2 = d2.kernel()  gives the following results: H0: Finitely generated module V/W over Integer Ring with invariants (2, 0) H1: Finitely generated module V/W over Integer Ring with invariants () H2: Free module of degree 2 and rank 0 over Integer Ring whereas ChainComplex([d0,d1,d2]).homology()  yields a different strucure. {0: Z, 1: Z, 2: C2, 3: 0} To maximize confusion, calculation by hand gives me H0=C2^2 x ZZ, H1=0, H2=0. I'd might have made some mistakes there, though. So I don't really konw how to interpret the results from Sage.