#12607: ChainComplex reports zero homology groups (depending on ChomP)
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Reporter: vbraun | Owner: jhpalmieri
Type: defect | Status: new
Priority: major | Milestone: sage-5.0
Component: algebraic topology | Keywords:
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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Comment(by jhpalmieri):
I'm not sure what you mean by irrelevant zeroes: if we chop off zeroes,
then should the reduced homology of the 2-sphere just be `{2: Z}`? That is
overly brief, I think. The answer
{{{
{0: 0, 1: 0, 2: Z, 3: 0}
}}}
for the homology of the fan includes dimensions 0-3 because those are the
dimensions in which the chain complex is nonzero. I think it makes sense
to include those groups, whether zero or not.
I think that the CHomP interface should be fixed so that we don't have
this issue: it can detect the upper and lower dimensions of the complex,
and then pad with zeroes as necessary. It might also make sense to add a
flag for the homology method to only return nontrivial groups.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12607#comment:1>
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