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nLab > Latest Changes: pushout-product

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    • CommentRowNumber1.
    • CommentAuthorUrs
    • CommentTimeMar 30th 2016
    • (edited Mar 30th 2016)

    Have added to pushout-product the statement (here) that pushout product □\Box of I 1I_1-cofibrations with I 2I_2-cofibrations lands in (I 1□I 2)(I_1\Box I_2)-cofibrations; and (here) the example of pushout products of the inclusions S n−1↪D nS^{n-1} \hookrightarrow D^n. Both without proof for the moment.

    • CommentRowNumber2.
    • CommentAuthorKarol Szumiło
    • CommentTimeSep 13th 2016

    Here is a terminology question. Does anyone know or have suggestions for a nice name for the right adjoint(s) to the pushout product? Whenever I have to name one, I usually end up saying something like “dual pushout product” which is a mouthful and difficult to work into sentences. As explained in Joyal-Tierney calculus they are sometimes called “left quotient” and “right quotient” which I don’t like, these constructions are nothing like quotients. (I can only imagine that this arose because when the tensor is join of simplicial sets, then the right adjoints are slices and they are sometimes notated like quotients. But that’s just a coincidence of notation.) I was also thinking about directly dualizing “pushout product” to something like “pullback hom” which is sort of descriptive but just doesn’t sound good to me.

    Can anyone help me with this riddle and suggest something that is both evocative and reasonably concise?

    • CommentRowNumber3.
    • CommentAuthorUrs
    • CommentTimeSep 13th 2016

    I have been saying “pullback powering” for it.

    • CommentRowNumber4.
    • CommentAuthorKarol Szumiło
    • CommentTimeSep 13th 2016

    Thanks for a suggestion. “Pullback power” is similar to my “pullback hom”, but I agree that it sounds less awkward. That’s probably a good name.

    • CommentRowNumber5.
    • CommentAuthorMike Shulman
    • CommentTimeSep 13th 2016

    That is pretty good. Is it recorded on the nLab anywhere?

    • CommentRowNumber6.
    • CommentAuthorUrs
    • CommentTimeSep 13th 2016
    • CommentRowNumber7.
    • CommentAuthorMike Shulman
    • CommentTimeSep 14th 2016

    Ok, I created a stub pullback power.

    • CommentRowNumber8.
    • CommentAuthorDmitri Pavlov
    • CommentTimeSep 14th 2016

    I actually used “pullback hom” in my papers.

    It may sound awkward, but it seems more descriptive than “pullback power”.

    • CommentRowNumber9.
    • CommentAuthorKarol Szumiło
    • CommentTimeSep 14th 2016

    The thing is that while right adjoints to some tensors are really hom objects, sometimes they are more general. I think “pullback power” is sufficiently generic to describe all such situations. Also “power” sounds to me more like an actual noun than “hom”.

    • CommentRowNumber10.
    • CommentAuthorDavid_Corfield
    • CommentTimeApr 13th 2017

    In A Generalized Blakers-Massey Theorem they call the dual of the pushout product, ’pullback hom’ (3.1.2).

    • CommentRowNumber11.
    • CommentAuthorUrs
    • CommentTimeApr 25th 2023

    touched wording and typesetting of the Definition-section (here, in particular I added a tikzcd-diagram for the definition)

    added the example of pushout-products of injections of sets, with an illustrating graphics (here)

    diff, v15, current

    • CommentRowNumber12.
    • CommentAuthorUrs
    • CommentTimeMay 20th 2023

    have spelled out the example (here) that any pushout-product of split epimorphisms is an isomorphism

    diff, v21, current

    • CommentRowNumber13.
    • CommentAuthorUrs
    • CommentTimeMay 20th 2023
    • (edited May 20th 2023)

    spelled out (here) in more detail the (fibers of the) pushout-product of maps of sets.

    diff, v22, current

    • CommentRowNumber14.
    • CommentAuthorUrs
    • CommentTimeMay 21st 2023

    added the example of pushout-product with an initial morphism (here)

    diff, v23, current

    • CommentRowNumber15.
    • CommentAuthorUrs
    • CommentTimeMay 21st 2023

    added (here) the example of pushout-product with an identity

    diff, v23, current

1 to 15 of 15

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