Not signed in (Sign In)

A discussion forum about contributions to the nLab wiki and related areas of mathematics, physics, and philosophy.

Want to take part in these discussions? Sign in if you have an account, or apply for one below

2-category 2-category-theory abelian-categories adjoint algebra algebraic algebraic-geometry algebraic-topology analysis analytic-geometry arithmetic arithmetic-geometry bundles calculus categories category category-theory chern-weil-theory cohesion cohesive-homotopy-theory cohesive-homotopy-type-theory cohomology colimits combinatorics complex complex-geometry computable-mathematics computer-science constructive cosmology deformation-theory descent diagrams differential differential-cohomology differential-equations differential-geometry digraphs duality elliptic-cohomology enriched fibration finite foundations functional-analysis functor gauge-theory gebra geometric-quantization geometry graph graphs gravity group group-theory harmonic-analysis higher higher-algebra higher-category-theory higher-differential-geometry higher-geometry higher-lie-theory higher-topos-theory homological homological-algebra homotopy homotopy-theory homotopy-type-theory index-theory integration integration-theory internal-categories itex k-theory lie lie-theory limit limits linear linear-algebra locale localization logic mathematics measure-theory modal modal-logic model model-category-theory monad monads monoidal monoidal-category-theory morphism motives motivic-cohomology nlab noncommutative noncommutative-geometry number-theory of operads operator operator-algebra order-theory pages pasting philosophy physics pro-object probability probability-theory quantization quantum quantum-field quantum-field-theory quantum-mechanics quantum-physics quantum-theory question representation representation-theory riemannian-geometry scheme schemes science set set-theory sheaf simplicial space spin-geometry stable-homotopy-theory string string-theory subobject superalgebra supergeometry svg symplectic-geometry synthetic-differential-geometry terminology theory topology topos topos-theory type type-theory universal variational-calculus

Vanilla 1.1.10 is a product of Lussumo. More Information: Documentation, Community Support.

If you want to take part in these discussions either sign in now (if you have an account), apply for one now (if you don't).

- Discussion Type
- discussion topicdifferences between CompLF v0 and v1
- Category Latest Changes
- Started by atmacen
- Comments 3
- Last comment by atmacen
- Last Active Jul 17th 2020

- Discussion Type
- discussion topiclist of journals publishing category theory
- Category Latest Changes
- Started by Mike Shulman
- Comments 44
- Last comment by Dmitri Pavlov
- Last Active Jul 17th 2020

- Discussion Type
- discussion topicdivision algebra and supersymmetry
- Category Latest Changes
- Started by Urs
- Comments 2
- Last comment by Urs
- Last Active Jul 17th 2020

added pointer to today’s

- Joás Venâncio, Carlos Batista,
*Two-Component Spinorial Formalism using Quaternions for Six-dimensional Spacetimes*(arXiv:2007.04296)

- Joás Venâncio, Carlos Batista,

- Discussion Type
- discussion topicpariah group
- Category Latest Changes
- Started by Urs
- Comments 3
- Last comment by nLab edit announcer
- Last Active Jul 17th 2020

- Discussion Type
- discussion topicAnthony Sudbery
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jul 17th 2020

for hyperlinking references at

*supersymmetry snd division algebras*

- Discussion Type
- discussion topicMarkov category
- Category Latest Changes
- Started by PaoloPerrone
- Comments 3
- Last comment by nLab edit announcer
- Last Active Jul 17th 2020

- Discussion Type
- discussion topicframe
- Category Latest Changes
- Started by Urs
- Comments 4
- Last comment by nLab edit announcer
- Last Active Jul 17th 2020

I have added some things to frame. Mostly duplicating things said elsewhere (at locale and at (0,1)-topos), but I need these statements to be at

*frame*itself.

- Discussion Type
- discussion topicPoisson-Lie T-duality
- Category Latest Changes
- Started by Urs
- Comments 23
- Last comment by Urs
- Last Active Jul 17th 2020

started a bare minimum at

*Poisson-Lie T-duality*, for the moment just so as to have a place to record the two original references

- Discussion Type
- discussion topictransferred model structure
- Category Latest Changes
- Started by Urs
- Comments 14
- Last comment by nLab edit announcer
- Last Active Jul 16th 2020

added to transferred model structure a simple remark in a subsection Enrichement on conditions that allow to transfer also an enriched model structure.

(The example I am thinking of is transferring the sSet-enriched model structure on cosimplicial rings to one on cosimplicial smooth algebras. But I won’t type that into the entry for the moment…)

- Discussion Type
- discussion topicSorin Dragomir
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jul 16th 2020

brief

`category:people`

-entry for hyperlinking references at*CR-manifold*

- Discussion Type
- discussion topicCR structure
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jul 16th 2020

discovered this old but empty entry. Made it point to

*CR-manifold*(it might just be cleared and “CR-structure” made a redirect for “CR-manifold”)

- Discussion Type
- discussion topicalgebra for an endofunctor
- Category Latest Changes
- Started by Urs
- Comments 54
- Last comment by Sam Staton
- Last Active Jul 16th 2020

I have added to algebra for an endofunctor a remark on the relation to algebras over free monads. While I think that’s pretty obvious, I notice that a) recently somebody has blogged about that here, b) here it says that it’s not true :-) (but I think it’s not meant to be read that way).

- Discussion Type
- discussion topicLorentzian orbifold
- Category Latest Changes
- Started by Urs
- Comments 3
- Last comment by Urs
- Last Active Jul 16th 2020

- Discussion Type
- discussion topicBoris Apanasov
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jul 16th 2020

brief

`category:people`

-entry for hyperlinking references at*conformal geometry*

- Discussion Type
- discussion topicconformal geometry
- Category Latest Changes
- Started by Urs
- Comments 2
- Last comment by Urs
- Last Active Jul 16th 2020

added pointer to

- Maks A. Akivis, Vladislav V. Goldberg,
*Conformal and Grassmann structures*, Differential Geom. Appl. 8 (1998) no. 2 177-203 (arXiv:math/9805107)

for discussion of conformal structure as G-structure

- Maks A. Akivis, Vladislav V. Goldberg,

- Discussion Type
- discussion topicspin structure
- Category Latest Changes
- Started by Urs
- Comments 5
- Last comment by Urs
- Last Active Jul 16th 2020

quick note at

*spin structure*on the characterization*over Kähler manifolds*

- Discussion Type
- discussion topicintelligent spam?
- Category Latest Changes
- Started by Guest
- Comments 22
- Last comment by Urs
- Last Active Jul 16th 2020

- Removed link from Eric Forgy that was placed by one TessWither. There was a little bit of other activity around that seemed to be just minor edits to create a smokescreen.

David Roberts

- Discussion Type
- discussion topicdinatural transformation
- Category Latest Changes
- Started by Mike Shulman
- Comments 4
- Last comment by David_Corfield
- Last Active Jul 16th 2020

Expanded dinatural transformation a little with examples and references.

- Discussion Type
- discussion topicdouble field theory
- Category Latest Changes
- Started by Luigi
- Comments 30
- Last comment by David_Corfield
- Last Active Jul 16th 2020

Hello,

I noticed DFT page has not been updated in a while and I added a couple of sections: some sketchy introductory material (analogy between Kaluza-Klein and DFT) and a little insight about a more rigorous geometrical formulation of DFT.

It is still quite sketchy but I would be happy to refine it.

PS: this is my first edit, I hope I played by the rules. And thank you all for this wiki

Luigi

- Discussion Type
- discussion topicKähler manifold
- Category Latest Changes
- Started by Urs
- Comments 2
- Last comment by Urs
- Last Active Jul 15th 2020

added publication data to

- Andrei Moroianu,
*Lectures on Kähler Geometry*, Cambridge University Press 2007 (arXiv:math/0402223 doi:10.1017/CBO9780511618666, pdf)

and pointer to section 11.1 there for Kaehler structures as torsion-free $U(n)$-structures

- Andrei Moroianu,

- Discussion Type
- discussion topicSpin(7) manifold
- Category Latest Changes
- Started by Urs
- Comments 4
- Last comment by Urs
- Last Active Jul 15th 2020

added this statement:

Let $X$ be a closed smooth manifold of dimension 8 with Spin structure. If the frame bundle moreover admits G-structure for

$G = Spin(7) \hookrightarrow Spin(8)$then the Euler class $\chi$, the second Pontryagin class $p_2$ and the cup product-square $(p_1)^2$ of the first Pontryagin class of the frame bundle/tangent bundle are related by

$8 \chi \;=\; 4 p_2 - (p_1)^2 \,.$

- Discussion Type
- discussion topicCalabi-Yau variety
- Category Latest Changes
- Started by Kevin Lin
- Comments 7
- Last comment by Urs
- Last Active Jul 15th 2020

I added a comment on the Calabi-Yau variety page about $c_1=0$. Does anyone know if it’s still true in the non-compact case?

Also, what’s the proper way to add questions/parenthetical remarks to n-Lab pages?

- Discussion Type
- discussion topicspecial holonomy
- Category Latest Changes
- Started by Urs
- Comments 5
- Last comment by Urs
- Last Active Jul 15th 2020

stub for special holonomy, just to record two references for the moment.

Also added a line to the Idea-section at holonomy that mentions holonomy group and special holonomy.

- Discussion Type
- discussion topicsymplectic manifold
- Category Latest Changes
- Started by Urs
- Comments 4
- Last comment by Urs
- Last Active Jul 15th 2020

I have expanded symplectic manifold a little

- Discussion Type
- discussion topicquaternion-Kähler manifold
- Category Latest Changes
- Started by Urs
- Comments 15
- Last comment by Urs
- Last Active Jul 15th 2020

- Discussion Type
- discussion topicG2 manifold
- Category Latest Changes
- Started by Urs
- Comments 5
- Last comment by Urs
- Last Active Jul 15th 2020

- Discussion Type
- discussion topicStefano Marchiafava
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jul 15th 2020

brief

`category:people`

-entry for hyperlinking references at*Sp(n).Sp(1)*, at*quaternionic manifold*and at*quaternion-Kähler manifold*

- Discussion Type
- discussion topicquaternionic manifold
- Category Latest Changes
- Started by James Francese
- Comments 8
- Last comment by Urs
- Last Active Jul 15th 2020

- Discussion Type
- discussion topic(infinity,1)-categorical hom-space
- Category Latest Changes
- Started by Urs
- Comments 2
- Last comment by Urs
- Last Active Jul 15th 2020

added pointer to

- Dan Dugger, David Spivak,
*Mapping spaces in quasi-categories*, Algebraic & Geometric Topology 11 (2011) 263–325 (arXiv:0911.0469, doi:10.2140/agt.2011.11.263)

- Dan Dugger, David Spivak,

- Discussion Type
- discussion topic(infinity,1)-category of (infinity,1)-categories
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jul 15th 2020

have added pointer to

Charles Rezk,

*A model for the homotopy theory of homotopy theory*, Trans. Amer. Math. Soc. 353 (2001), 973-1007 (arXiv:math/9811037, doi:10.1090/S0002-9947-00-02653-2)Julia Bergner,

*Three models for the homotopy theory of homotopy theories*, Topology Volume 46, Issue 4, September 2007, Pages 397-436 (arXiv:math/0504334, doi:10.1016/j.top.2007.03.002)