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    • Some time ago I started a stub characteristic variety to record few references, mainly in D-module context. Regarding that the related notion of a characteristic ideal also appears in the treatment of Iwasawa polynomial and Alexander polynomial which Urs wants to understand from the point of view of connections and differential refinements of cohomology, maybe we should do some effort to make some pages which will connect various notions of characteristic ideals and their loci across various subjects. I just recorded

      • Andrea Bandini, Francesc Bars, Ignazio Longhi, Characteristic ideals and Iwasawa theory, arxiv/1310.0680; Characteristic ideals and Selmer groups, arxiv/1404.2788

      at characteristic ideal for the version in the context of Iwasawa theory.

    • gave Langlands correspondence an actual Idea-section.

      (Am in a rush and on a horrible wifi connection. Need to proof-read and add more links later.)

    • started a minimum at Euler product, the main point being for the moment to mention briefly how Euler product forms naturally appears from the point of view of adelic integration/Iwasawa-Tate theory.

    • I have renamed the entry pretriangulated dg-category to stable dg-category. I think this is a logical move that emphasizes the close relationship with the notions of stable (infinity,1)-category and stable model category. If anyone disagrees I would be interested to hear why. I have also edited the body of the page to give an exposition more in line with modern references like Cisinski-Tabuada. However I have adopted the term dg-presheaf for what is usually called (right) dg-module. This seems much more natural to me, but again I am open to hearing any arguments against it. When I get a minute I will also update the entry dg-category to match the conventions of this page.

      Also, I never liked the term “quasi-equivalence”. I think that this should just be called equivalence of dg-categories, or maybe Dwyer-Kan equivalence if this is too ambiguous. Any thoughts?

    • @Urs: I do not quite agree with the sentence “This is unrelated to other notions of monads” in Beilinson monad.

      One can indeed view the Beilinson monad as the monad of an adjoint equivalence between ℭ𝔬𝔥 n\mathfrak{Coh} \mathbb{P}^n (interpreted as the heart of D b nD^b \mathbb{P}^n and some category of linear complexes over an exterior algebra (the Koszul dual of the Cox ring of n\mathbb{P}^n).

    • At differential cohesion there used to be the statement that every object XX canonically has a “spectrum” given by (Sh H(X),𝒪 X)(Sh_{\mathbf{H}}(X), \mathcal{O}_X), but the (simple) argument that 𝒪 X\mathcal{O}_X indeed satisfies the axioms of a structure sheaf used to be missing. I have now added it here.

    • added references.

      Any book that develops a bit of algebraic geometry of non-unital commutative rings or one that discusses what would be hte major things that break?

    • Corrected the associated monad in reflective subcategory:

      ---
      The monad (Q^* Q_*,Q^*\varepsilon Q_*,\eta) associated with the adjunction
      ->
      The monad (Q_* Q_^*,\varepsilon,Q_* \eta Q_^*) associated with the adjunction
      ---
    • I added a clarifying clause to infinity-field so it now reads

      The Morava K-theory A-∞ rings K(n)K(n) are essentially the only A A_\infty-fields. See at Morava K-theory – As infinity-Fields, where K(0)HK(0) \simeq H \mathbb{Q} and we define K()K(\infty) as H𝔽 pH \mathbb{F}_p.

      This is from Lurie’s lectures. What precisely does he mean? He says in lecture 24 that for kk any field that its E-M spectrum HkH k is an infinity-field, so the “essentially” is doing some work. Is the idea that all infinity-fields are K(n)K(n)-modules (cor 10, lecture 25), so the K(n)K(n) essentially cover things?

      On another point, would there be a higher form of the rational/p-adic fracturing of \mathbb{Z}, involving the K(n)K(n)?

    • started completion of a module, for the moment mainly so as to record a bunch of basic definitions and facts about completion of \infty-modules from DAG12

    • I have given the notion of canonical transformation as used in Hamiltonian mechanics its own brief page.

      So in particular I removed the redirect of that term to canonical morphism and instead added disambiguation lines on the top of both entries. I think this is justified: the term “canonical transformation” has been standard since ancient times in Hamiltonian mechanics and is in each and every textbook on the matter. On the other hand the same term as referring to canonical morphisms was mainly the proposal of one single person in category theory, and never caught up much, I think. (Also I find the term ill-motivated in category theory in the first place).

      Therefore, while the disambiguation redirects ensure that both notions still can be found, I think it is clear that the default meaning must be that in Hamiltonian mechanics.

    • I have worked on the entry synthetic differential infinity-groupoid;

      • added a brief remark in the Idea section;

      • spelled out statement and proof that SynthDiffGrpdSynthDiff \infty Grpd is totally \infty-connected over SmoothGrpdSmooth \infty Grpd;

      • began some discussion on how the induced relative fundamental \infty-groupoid functor is Π inf\mathbf{\Pi}_{inf}: the infinitesimal path \infty-groupoid functor, such that Π inf(X)\mathbf{\Pi}_{inf}(X) is the de Rham space of XX and a morphism Π inf(X)Mod\mathbf{\Pi}_{inf}(X) \to \infty Mod an \infty-stack of D-modules on XX. But this deserves more discussion.

      Concerning the writeup of the second point I had myself confused about the direction of one of the arrows for a while. Hope I got it right now.

    • Unfortunately, I am lacking chocolat medals (as well as the authority to award them), but thanks to the author (presumably Todd) who graced Karoubi envelope with the proof that smooth manifolds result from open sets by idempotent splitting.

      I have added a reference to Lawvere’s Perugia notes where this appeared as an exercise.

      Entre parenthèses: it appears to me that it’d be better to have the proof at the page for smooth manifolds and to mention the result only at Karoubi envelope as I think this is kind of a butterfly at Karoubi though a beautiful one but an important result for manifolds.

    • I created generalized uniform structures - table in the style of all of those tables that Urs makes and included it on most of the relevant pages. (I left the pages on the simplest concepts, the binary relations.)

      I hope that the headers “monad on an object” and “monad on a pro-object” are accurate. These should be objects in an equipment, I think. Perhaps Mike can help me figure out what equipments are relevant here.

    • I have greatly expanded the basic definition at prometric space to show other ways to look at the concept.

    • Started adjoint lifting theorem. For now, it only includes a version for lifting left adjoints (I still haven’t read Johnstone’s 1975 paper for the case of right adjoints). I hope there is no substantial error in the appliaction for cocompleteness.

    • Fumbling around Jonsson-Tarski topos I’ve created entries on Thompson group and Higman’s theorem. Basically some links to further material. As Jónsson-Tarski seems to bring together a lot of stuff from different fields, I think we should have also some material on Tom’s work on self-similarity here.

    • I created ordinal subdivision to get rid of a grey link in subdivision, but it just gives a reference to the paper by Phil Ehlers and myself. I need to check at ordinal sum to see what was put there before continuing.

    • I have expanded on ETCC and introduced a section on ET2CC which I could occasionally fill with Mike’s ideas from MO in case all n-categorists are lying on the beach. I would also propose to replace the current ’idea’ section with what is right now called ’overview’ or some reworking of that.

      I think it best to keep everything in a single entry given that these ideas on ETCC with or without 2 meet only a limited enthusiasm in the HOTT times.

    • I’ve created a page for the Witt vectors. It seems that even with all that I wrote here (don’t worry I had a set of about 10 blog entries I wrote a few months ago that I just condensed, so I didn’t write this whole thing tonight) there are all sorts of things still missing here. The Witt functor is mention at Lambda-ring and there seems to be connections to the field with one element (?!). I just needed to refer to Witt vectors in the next few pages I want to make, so I decided this had to come first. Dieudonne module will need it and obviously Witt cohomology will need it.

    • killed a spam page, now called spam

    • The entry Borel-Weil theorem mentions extensions of the theorem to quantum groups, without however giving a reference. I just got an email asking for these.

      The statement dates from August 19, 2009, due to Zoran.

    • I began adding proofs of Lemma 1-4 to the page transfinite construction of free algebras. The layout of the two array environment has to be fixed; proof of 3-4 to be added.

      Any help/suggestion is extremely appreciated!

    • Someone (anonymous) has created an empty page oon finite dimensional vector spaces.

    • needed to point to restricted product, so I created a bare (and unsophisticated) minimum

    • I mostly wanted to record the correct meaning of this term. Then maybe later I can use this as a reference to fix Wikipedia (^_^). But there's a bit more here too.

      imaginary number

    • Edited biholomorphic function to follow the same format as diffeomorphism. In particular, this means that I qualified biholomorphic function to refer only to maps between complex manifolds. Is there a more general definition of holomorphic functions between complex analytic spaces?