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    • I understood that the old terminology was ’projective system’, and ’projective limit’ refereed to the limit of a projective system. Can anyone confirm that? if I am right the present entry is slightly incorrect, but this needs checking first before changing it.

    • Created this page, since references are somewhat hard to find.

      Adrien Brochier

      v1, current

    • I added references to John Baez’s two blog posts on The Geometric McKay Correspondence, Part I, Part II.

      I hadn’t realised the length of legs in the Dynkin diagrams corresponds to the stabilizer order on vertices, edges, faces in the corresponding Platonic solid. So 2,3,5 for E 8E_8 and the icosahedron.

      diff, v5, current

    • added [ISBN 978-3-642-61458-3] (

      diff, v5, current

    • In the definition, the article states "every object in C is a small object (which follows from 2 and 3)". The bracketed remark doesn't seem quite right to me, since neither 2 nor 3 talk about smallness of objects. Presumably this should better be phrased as in A.1.1 of HTT, "assuming 3, this is equivalent to the assertion that every object in S is small".

      Am I right? I don't (yet) feel confident enough with my category theory to change this single-handedly.
    • Under definition 1 of salamander lemma, I fixed a mistake in the definition of A A_\Box where there was a direct sum of two submodules, where there needed to be a sum (i.e., join) instead.

    • Made a few additions to preimage. Added missing word; added a brief mention of the widely-known general reason for the good preservation-properties of this endofunctor.

      The mention of these properties had already been there in preimage, but a reason was still missing. My parenthetical remark should perhaps be expanded and harmonized with existing relevant material on the nLab ( f\forall_f and f\exists_f are already well-documented on some pages), but this requires more care than I can apply to it today. Intend to return to the remark before long.

    • Page created, but author did not leave any comments.


      v1, current

    • made page name singular, added references on Wilson line observables

      diff, v2, current

    • starting a bare references-list entry, to be !includeed in the References-sections of relevant entries

      v1, current

    • Strangely, we don’t seem to have an nForum discussion for probability theory.

      I added a reference there to

      It replaces the category of measurable spaces, which isn’t cartesian closed, with the category of quasi-Borel spaces, which is. As they point out in section IX, what they’re doing is working with concrete sheaves on an established category of spaces, rather like the move to diffeological spaces.

      [Given the interest in topology around these parts at the moment, we hear of ’C-spaces’ as generalized topological spaces arising from a similar sheaf construction in C. Xu and M. Escardo, “A constructive model of uniform continuity,” in Proc. TLCA, 2013.]

    • am giving this its own entry – but just starting, nothing much here yet…

      v1, current

    • I worked on synthetic differential geometry:

      I rearranged slightly and then expanded the "Idea" section, trying to give a more comprehensive discussion and more links to related entries. Also added more (and briefly commented) references. Much more about references can probably be said, I have only a vague idea of the "prehistory" of the subject, before it became enshrined in the textbooks by Kock, Lavendhomme and Moerdijk-Reyes.

      Also, does anyone have an electronic copy of that famous 1967 lecture by Lawvere on "categorical dynamics"? It would be nice to have an entry on that, as it seems to be a most visionary and influential text. If I understand right it gave birth to topos theory, to synthetic differential geometry and all that just as a spin-off of a more ambitious program to formalize physics. If I am not mistaken, we are currently at a point where finally also that last bit is finding a full implmenetation as a research program.

    • @Todd. Thanks for correcting my atrocious English!

      Does anyone have any ideas as to how we could provide a bit more for this entry?

    • now that Mike announced a proof, and hearing Steve’s comment, I felt it would be nice to have a name for conjecture (partially) proven thereby, for ease of communiucating it to the rest of the world. Just a start, please edit the entry as need be.

      v1, current

    • Add a reference for string diagrams in closed monoidal categories


      diff, v42, current