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-categories 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 comma complex-geometry computable-mathematics computer-science constructive cosmology deformation-theory descent diagrams differential differential-cohomology differential-equations differential-geometry differential-topology digraphs duality education elliptic-cohomology enriched fibration finite foundations functional-analysis functor galois-theory gauge-theory gebra geometric-quantization geometry graph graphs gravity grothendieck 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 infinity integration integration-theory k-theory lie lie-theory limit limits linear linear-algebra locale localization logic mathematics measure-theory modal-logic model model-category-theory monoidal monoidal-category-theory morphism motives motivic-cohomology multicategories nonassociative noncommutative noncommutative-geometry number-theory of operads operator operator-algebra order-theory pasting philosophy physics planar 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 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 topicsharp map
- Category Latest Changes
- Started by Urs
- Comments 8
- Last comment by Mike Shulman
- Last Active Jan 26th 2019

created a bare minimum at

*sharp map*

- Discussion Type
- discussion topicskyrmion
- Category Latest Changes
- Started by Urs
- Comments 7
- Last comment by Urs
- Last Active Jan 25th 2019

- Discussion Type
- discussion topicright-handed neutrino
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 25th 2019

- Discussion Type
- discussion topiccomposite Higgs model
- Category Latest Changes
- Started by Urs
- Comments 2
- Last comment by Urs
- Last Active Jan 25th 2019

a stub, on occasion of today’s

- Oliver Witzel,
*Review on Composite Higgs Models*(arXiv:1901.08216)

and to provide the previously missing link at

*flavour anomaly*for- David Marzocca,
*Addressing the B-physics anomalies in a fundamental Composite Higgs Model*, JHEP07(2018)121 (arXiv:1803.10972)

- Oliver Witzel,

- Discussion Type
- discussion topicanomalous magnetic moment
- Category Latest Changes
- Started by Urs
- Comments 7
- Last comment by David_Corfield
- Last Active Jan 24th 2019

there is an old article (Berends-Gastman 75) that computes the 1-loop corrections due to perturbative quantum gravity to the anomalous magnetic moment of the electron and the muon. The result turns out to be independent of the choice of (“re”-)normalization (hence what they call “finite”).

I have added a remark on this in the $(g-2)$-entry here and also at

*quantum gravity*here.

- Discussion Type
- discussion topicquantum gravity
- Category Latest Changes
- Started by Urs
- Comments 6
- Last comment by Urs
- Last Active Jan 24th 2019

in order to satisfy links, but maybe really in procrastination of other duties, I wrote something at quantum gravity

- Discussion Type
- discussion topicIsing model
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 24th 2019

added pointer to

- Connor Behan,
*Bootstrapping the long-range Ising model in three dimensions*, Journal of Physics A: Mathematical and Theoretical, Volume 52, Number 7 (arXiv:1810.07199, doi:10.1088/1751-8121/aafd1b)

- Connor Behan,

- Discussion Type
- discussion topicnuclear physics
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 24th 2019

- Discussion Type
- discussion topicrho meson
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 24th 2019

some minimum, currently so as to record

- Carlos Naya, Paul Sutcliffe,
*Skyrmions and clustering in light nuclei*, Phys. Rev. Lett. 121, 232002 (2018) (arXiv:1811.02064)

- Carlos Naya, Paul Sutcliffe,

- Discussion Type
- discussion topicPaul Sutcliffe
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 24th 2019

brief

`category:people`

-entry for hyperlinking references at*skyrmion*,*atomic nucleus*

- Discussion Type
- discussion topiccomplex surface
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 24th 2019

- Discussion Type
- discussion topicatomic number
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 24th 2019

started some minimum, to satisfy links

same comment applies as I just made at

*chemical element*:added pointer to

- Michael Atiyah, Nicholas Manton,
*Complex Geometry of Nuclei and Atoms*(arXiv:1609.02816)

For a while I thought that this proposal is completely crazy. But in view of the established success of Skyrmion models for atomic nuclei and in particular with these viewed within the Sakai-Sugimoto model, it doesn’t seem completely crazy anymore. I still think it must be admitted that the concrete evidence that there is an actual model of nuclie by complex surfaces is extremely weak and very vague, but I can see now why it is interesting and maybe even tantalizing.

- Michael Atiyah, Nicholas Manton,

- Discussion Type
- discussion topicchemical element
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 24th 2019

changed page name to singluar

added mentioning of atomic number

added pointer to

- Michael Atiyah, Nicholas Manton,
*Complex Geometry of Nuclei and Atoms*(arXiv:1609.02816)

For a while I thought that this proposal is completely crazy. But in view of the established success of Skyrmion models for atomic nuclei and in particular with these viewed within the Sakai-Sugimoto model, it doesn’t seem completely crazy anymore. I still think it must be admitted that the concrete evidence that there is an actual model of nuclie by complex surfaces is extremely weak and very vague, but I can see now why it is interesting and maybe even tantalizing.

- Michael Atiyah, Nicholas Manton,

- Discussion Type
- discussion topiccarbon
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 24th 2019

- Discussion Type
- discussion topicsemicartesian monoidal category
- Category Latest Changes
- Started by nLab edit announcer
- Comments 2
- Last comment by Richard Williamson
- Last Active Jan 24th 2019

- Discussion Type
- discussion topicnominal set
- Category Latest Changes
- Started by Richard Williamson
- Comments 1
- Last comment by Richard Williamson
- Last Active Jan 24th 2019

- Discussion Type
- discussion topicNicholas Manton
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 24th 2019

- Discussion Type
- discussion topicleptoquark
- Category Latest Changes
- Started by Urs
- Comments 32
- Last comment by Urs
- Last Active Jan 23rd 2019

- Discussion Type
- discussion topicJohn Wheeler
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 23rd 2019

added today’s

- Kip Thorne,
*John Archibald Wheeler: A Biographical Memoir*(arXiv:1901.06623)

- Kip Thorne,

- Discussion Type
- discussion topicsimplicial object
- Category Latest Changes
- Started by Urs
- Comments 7
- Last comment by Mike Shulman
- Last Active Jan 23rd 2019

added to simplicial object a section on the canonical simplicial enrichment and tensoring of $D^{\Delta^{op}}$ for $D$ having colimits and limits.

- Discussion Type
- discussion topicgeometric realization
- Category Latest Changes
- Started by Todd_Trimble
- Comments 28
- Last comment by Mike Shulman
- Last Active Jan 23rd 2019

I wrote out a proof that geometric realization of simplicial sets valued in compactly generated Hausdorff spaces is left exact, using essentially the observation that simplicial sets are the classifying topos for intervals, combined with various soft topological arguments. I left a hole to be plugged, that geometric realizations are CW complexes. I also added a touch to filtered limit, and removed a query of mine from triangulation.

I wanted a “pretty proof” for this result on geometric realization, centered on the basic topos observation (due to Joyal). I was hoping Johnstone did this himself in his paper on “a topological topos”, but I couldn’t quite put it together on the basis of what he wrote, so my proof is sort of “homemade”. I wouldn’t be surprised if it could be made prettier still. [Of course, “pretty” is in the eye of the beholder; mainly I want conceptual arguments which avoid fiddling around with the combinatorics of shuffle products (which is what I’m guessing Gabriel and Zisman did), decomposing products of simplices into simplices.]

- Discussion Type
- discussion topicTommaso Dorigo
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 23rd 2019

brief

`category:people- entry`

for hyperlinking references at*statistical significance*,*flavour anomaly*

- Discussion Type
- discussion topicLouis Lyons
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 23rd 2019

brief

`category:people`

-entry for hyperlinking references at*statistical significance*,*flavour anomaly*and*anomalous magnetic moment*

- Discussion Type
- discussion topicMcKay correspondence
- Category Latest Changes
- Started by David_Corfield
- Comments 8
- Last comment by Urs
- Last Active Jan 23rd 2019

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 $E_8$ and the icosahedron.

- Discussion Type
- discussion topicrecollement
- Category Latest Changes
- Started by zskoda
- Comments 23
- Last comment by jonrowlands
- Last Active Jan 23rd 2019

I have created the entry recollement. Adjointness, cohesiveness etc. lovers should be interested.

- Discussion Type
- discussion topicRandall-Sundrum model
- Category Latest Changes
- Started by Urs
- Comments 4
- Last comment by Urs
- Last Active Jan 22nd 2019

- Discussion Type
- discussion topicAndreas Crivellin
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 22nd 2019

brief

`category:people`

-entry for hyperlinking references at*flavour anomaly*,*leptoquark*and*electric dipole moment*

- Discussion Type
- discussion topicquiver gauge theory
- Category Latest Changes
- Started by Urs
- Comments 5
- Last comment by Urs
- Last Active Jan 22nd 2019

started something at

*quiver gauge theory*; some very basic sentences on the Idea of it all, and some bare minimum of references.This is a vast subject, and clearly that entry deserves to be expanded much further.

In the course of creating this I needed to create brief entries

*B-brane*and*exceptional collection*.

- Discussion Type
- discussion topicMcKay quiver
- Category Latest Changes
- Started by Urs
- Comments 3
- Last comment by Urs
- Last Active Jan 22nd 2019

- Discussion Type
- discussion topicKaluza-Klein monopole
- Category Latest Changes
- Started by Urs
- Comments 3
- Last comment by Urs
- Last Active Jan 22nd 2019

I have tried to clarify a bit more at

*Kaluza-Klein monopole*, and at*D6-brane*