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    • I am trying to collect citable/authorative references that amplify the analog of the mass gap problem in particle phenomenology, where it tramslates into the open problem of computing hadron masses and spins from first principles (due to the open problem of showing existence of hadrons in the first place!).

      This is all well and widely known, but there is no culture as in mathematics of succinctly highlighting open problems such that one could refer to them easily.

      I have now created a section References – Phenomenology to eventually collect references that come at least close to making this nicely explicit. (Also checked with the PF community here)

      diff, v4, current

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

      v1, current

    • stub entry for the moment, to satisfy links

      v1, current

    • I am moving the following old query box exchange from orbifold to here.

      old query box discussion:

      I am confused by this page. It starts out by boldly declaring that “An orbifold is a differentiable stack which may be presented by a proper étale Lie groupoid” but then it goes on to talk about the “traditional” definition. The traditional definition definitely does not view orbifolds as stacks. Neither does Moerdijk’s paper referenced below — there orbifolds form a 1-category.

      Personally I am not completely convinced that orbifolds are differentiable stacks. Would it not be better to start out by saying that there is no consensus on what orbifolds “really are” and lay out three points of view: traditional, Moerdijk’s “orbifolds as groupoids” (called “modern” by Adem and Ruan in their book) and orbifolds as stacks?

      Urs Schreiber: please, go ahead. It would be appreciated.

      end of old query box discussion

    • Definition of extensional PiPi-type structure taken from Natural models of homotopy type theory

      Should we develop how to get application, β\beta and η\eta here or should we leave it to the interpretation ?

      v1, current

    • Created categorical model of dependent types, describing the various different ways to strictify category theory to match type theory and their interrelatedness. I wasn’t sure what to name this page — or even whether it should be part of some other page — but I like having all these closely related structures described in the same place.

    • I fixed a broken link to Guy Moore’s lectures

      diff, v9, current

    • Added missing axiom. To see that an axiom like that is necessary, just observe that in the former formulation (without the first assumption) the requirements for meet and join were symmetric.

      diff, v25, current

    • added pointer to

      • R. P. Brent, J. van de Lune, H. J. J. te Riele and D. T. Winter, On the Zeros of the Riemann Zeta Function in the Critical Strip. II, Mathematics of Computation Mathematics of Computation Vol. 39, No. 160 (Oct., 1982), pp. 681-688 (doi:10.2307/2007345 )

      for computer-checks of the Riemann hypothesis. (there are probably more recent such?)

      diff, v8, current

    • Created semi-simplicial set, mainly as a repository for some terminological remarks. I would welcome anyone more knowledgeable about the history to correct or improve it!

    • Added some remark on the order of a semiring. Actually, does anybody know if any semiring embedds into a semifield?

      diff, v5, current

    • Created page with some basic definitions.

      v1, current

    • some minimum, see the related edit announcement here

      v1, current

    • The former version redirected to basically to theory, where in the idea section the first link went right back to this entry.

      diff, v2, current

    • added a little bit more text and pointers, to make this entry a little less stubby

      diff, v5, current

    • created computational trinitarianism, combining a pointer to an exposition by Bon Harper (thanks to David Corfield) with my table logic/category-theory/type-theory.

    • Move to full name; correct relationship to tangent.

      diff, v2, current

    • I do not understand the entry G-structure. G-structure is, as usual, defined there as the principal GG-subbundle of the frame bundle which is a GL(n)GL(n)-principal bundle. I guess this makes sense for equivariant injections along any Lie group homomorphism GGL(n)G\to GL(n). The entry says something about spin structure, warning that the group Spin(n)Spin(n) is not a subgroup of GL(n)GL(n). So what is meant ? The total space of a subbundle is a subspace at least. Does this mean that I consider the frame bundle first as a (non-principal) Spin(n)Spin(n)-bundle by pulling back along a fixed noninjective map Spin(n)GL(n)Spin(n)\to GL(n) and then I restrict to a chosen subspace on which the induced action of Spin group is principal ?