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    • CommentRowNumber1.
    • CommentAuthorMike Shulman
    • CommentTimeSep 8th 2015

    I thought I remembered some discussion at some point of “co-concrete objects”, those for which AA\flat A \to A is surjective. But now I can’t find it on the lab or the forum. Is my memory faulty?

    • CommentRowNumber2.
    • CommentAuthorUrs
    • CommentTimeSep 8th 2015
    • (edited Sep 8th 2015)

    maybe co-concrete object?

    [edit: I just went and fixed an evident typo there, and I have made “coconcrete object” redirect to the entry]

    • CommentRowNumber3.
    • CommentAuthorMike Shulman
    • CommentTimeSep 8th 2015

    Thanks. Apparently with the hyphen it doesn’t turn up in search.

    • CommentRowNumber4.
    • CommentAuthorTodd_Trimble
    • CommentTimeSep 8th 2015

    I wonder to what extent hyphenation turns up glitches? Recently I wrote Chu-Vandermonde identity but the link from here didn’t work. Testing it now, it still doesn’t, although I can force the issue by a copy-and-paste: see here.

    • CommentRowNumber5.
    • CommentAuthorUrs
    • CommentTimeSep 8th 2015
    • (edited Sep 8th 2015)

    • CommentRowNumber6.
    • CommentAuthorUrs
    • CommentTimeSep 8th 2015
    • (edited Sep 8th 2015)

    Todd, that’s the hyphen bug, first discussed here.

    The workaround that I apply whenever I see the bug is this: I copy-and-paste the text of the grayed-link-that-ought-to-work into a redirect in the entry.

    To the naked eye this will look exactly like the entry title or like existing redirects, but I suppose internally the hyphen sometimes gets represented by different codes.

    [edit: Hm, actually in the case you point to the two hyphens do look different, even to the naked eye. In that case it’s not a bug, just a nuisance. But just earlier today I saw the actual bug elsewhere, it’s still there, too. In any case, hyphens require special attention.]

    • CommentRowNumber7.
    • CommentAuthorTodd_Trimble
    • CommentTimeSep 8th 2015

    Urs, thanks for the info. I also saw that the hyphens looked different, but saw nothing I did that would account for that.

    I’ll remember your workaround, but also note that ordinarily I say Vandermonde identity or Vandermonde convolution identity anyway, so this particular case is no big deal.