#15245: Pfaffian of a skew-symmetric matrix
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Reporter: darij | Owner:
Type: enhancement | Status:
Priority: major | needs_review
Component: combinatorics | Milestone: sage-5.13
Keywords: matrix, sage-combinat, | Resolution:
pfaffian | Merged in:
Authors: Darij Grinberg | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: #14117 | Stopgaps:
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Comment (by nbruin):
Replying to [comment:13 darij]:
> I've given the {{{is_skew_symmetric}}} method an additional keyword
variable now. All the rest is OK?
That keyword should really be `is_alternating`, so the more appropriate
thing would be to supply a method `is_alternating`.
If pfaffians need alternating rather than skew-symmetric (I haven't
checked) then the confusion in terminology just comes from the fact that
people looking at pfaffians haven't considered characteristic 2. That kind
of thing happens all the time, and it's the kind of thing that computer
algebra systems need to be a little more pedantic about than math
literature, since you don't get to say "in this paper, with <THIS> we mean
<SOMETHING ELSE>".
It may well be that pfaffians are simply not all that useful in
characteristic 2, so that people didn't bother with them (Cayley certainly
wouldn't have).
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Ticket URL: <http://trac.sagemath.org/ticket/15245#comment:14>
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