#24725 closed enhancement (fixed)

Make power poset a meet-semilattice

Reported by: jmantysalo Owned by:
Priority: minor Milestone: sage-8.2
Component: combinatorics Keywords:
Cc: tscrim Merged in:
Authors: Jori Mäntysalo Reviewers: Frédéric Chapoton
Report Upstream: N/A Work issues:
Branch: 6d0bd62 (Commits) Commit: 6d0bd62e5e71c3b635e3838eea94d480ad1bfb99
Dependencies: Stopgaps:

Description

Power poset is meet-semilattice, of course -- meet of elements is the "intersection" of posets.

Change History (8)

comment:1 Changed 22 months ago by jmantysalo

  • Branch set to u/jmantysalo/power-lattice

comment:2 Changed 22 months ago by jmantysalo

  • Cc tscrim added
  • Commit set to 6d0bd62e5e71c3b635e3838eea94d480ad1bfb99
  • Status changed from new to needs_review

New commits:

6d0bd62Return type of PowerPoset().

comment:3 follow-up: Changed 22 months ago by chapoton

Ok, looks good. Is this poset selfdual, or not ?

Is the PowerPoset the same as the picture on page 8 of

https://arxiv.org/pdf/1701.07995.pdf

?

comment:4 in reply to: ↑ 3 Changed 22 months ago by jmantysalo

Replying to chapoton:

Ok, looks good. Is this poset selfdual, or not ?

Is the PowerPoset the same as the picture on page 8 of

https://arxiv.org/pdf/1701.07995.pdf

?

No, this is different thing. Elements of this poset are posets. The bottom element is the antichain on elements 1..n (actually 0..n-1), and maximal elements are all n! chains.

comment:5 Changed 22 months ago by chapoton

  • Reviewers set to Frédéric Chapoton
  • Status changed from needs_review to positive_review

ok, then

comment:6 follow-up: Changed 22 months ago by mantepse

Wouldn't it be good to add a line to the doc explaining why it is a semilattice?

comment:7 in reply to: ↑ 6 Changed 22 months ago by jmantysalo

Replying to mantepse:

Wouldn't it be good to add a line to the doc explaining why it is a semilattice?

It would.

Volker doesn't like modifying tickets already in positive review, so I will combine this with some other changes.

comment:8 Changed 22 months ago by vbraun

  • Branch changed from u/jmantysalo/power-lattice to 6d0bd62e5e71c3b635e3838eea94d480ad1bfb99
  • Resolution set to fixed
  • Status changed from positive_review to closed
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