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- Discussion Type
- discussion topicEncyclopedia of Mathematical Physics 2nd ed
- Category Latest Changes
- Started by Urs
- Comments 19
- Last comment by Urs
- Last Active Jan 18th 2024

starting a

`category:reference`

-entry.Just a single item so far, but this entry should incrementally grow as more preprints appear (similar to what we have been doing at

*Handbook of Quantum Gravity*and similar entries).I know that a soft deadline for submissions of at least one of the sections is this December, so I am guessing this is planned to appear in 2024.

- Discussion Type
- discussion topiclarge N limit
- Category Latest Changes
- Started by zskoda
- Comments 20
- Last comment by Urs
- Last Active Jan 18th 2024

We should have an entry on large N limit gradually. But sometimes it can be treated as a semiclassical limit. I quoted a reference by Yaffe where I originally read of that approach to the entry semiclassical expansion.

- Discussion Type
- discussion topichigher curvature correction
- Category Latest Changes
- Started by Urs
- Comments 13
- Last comment by Urs
- Last Active Jan 18th 2024

- Discussion Type
- discussion topicfixed point
- Category Latest Changes
- Started by Todd_Trimble
- Comments 21
- Last comment by varkor
- Last Active Jan 17th 2024

Made a start on an article fixed point, which might need to be farmed out to “sub-pages” (as this is a mighty big general topic).

- Discussion Type
- discussion topicentwining structure
- Category Latest Changes
- Started by zskoda
- Comments 16
- Last comment by mattecapu
- Last Active Jan 17th 2024

Cleaning or creating entries related to corings (e.g. grouplike element, Sweedler coring) and entwining structures, including personal entries Gabriella Böhm, Tomasz Brzeziński etc. On the edge of this activity I am interested in the relation between classical correspondence between flat connections and the descent data in abelian context; it could be related to the theorem of Urs and Konrad on the relation between descent data and transport functors in global context. I would like to know the parallel precisely.

- Discussion Type
- discussion topicalgebra for a profunctor
- Category Latest Changes
- Started by varkor
- Comments 1
- Last comment by varkor
- Last Active Jan 17th 2024

Added a cross-reference to algebra for an endomorphism.

- Discussion Type
- discussion topicfield with one element
- Category Latest Changes
- Started by Urs
- Comments 37
- Last comment by Urs
- Last Active Jan 17th 2024

created field with one element with two useful references

- Discussion Type
- discussion topicreal numbers type
- Category Latest Changes
- Started by nLab edit announcer
- Comments 1
- Last comment by nLab edit announcer
- Last Active Jan 16th 2024

- Discussion Type
- discussion topicdouble category
- Category Latest Changes
- Started by John Baez
- Comments 26
- Last comment by varkor
- Last Active Jan 16th 2024

- I added more info on pseudo double categories and double bicategories to double category. I also simplified the picture of a square, which had been bristling with scary unnecessary detail. There's a slight blemish in the left vertical arrow, which I can't see how to fix.

- Discussion Type
- discussion topicSpin(7) manifold
- Category Latest Changes
- Started by Urs
- Comments 5
- Last comment by Urs
- Last Active Jan 16th 2024

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 topicKosta Došen
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 16th 2024

- Discussion Type
- discussion topicM-Theory and Mathematics
- Category Latest Changes
- Started by Urs
- Comments 15
- Last comment by Urs
- Last Active Jan 15th 2024

- Discussion Type
- discussion topicmoduli spaces -- contents
- Category Latest Changes
- Started by Urs
- Comments 3
- Last comment by Urs
- Last Active Jan 15th 2024

- Discussion Type
- discussion topicclan
- Category Latest Changes
- Started by David_Corfield
- Comments 10
- Last comment by nLab edit announcer
- Last Active Jan 15th 2024

- Discussion Type
- discussion topichomological category
- Category Latest Changes
- Started by zskoda
- Comments 8
- Last comment by Ali Caglayan
- Last Active Jan 14th 2024

New entry homological category.

- Discussion Type
- discussion topicchange of enriching category
- Category Latest Changes
- Started by Urs
- Comments 12
- Last comment by nLab edit announcer
- Last Active Jan 14th 2024

- Discussion Type
- discussion topicIan Putnam
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 14th 2024

- Discussion Type
- discussion topicC-star-algebra
- Category Latest Changes
- Started by Urs
- Comments 4
- Last comment by Urs
- Last Active Jan 14th 2024

- Discussion Type
- discussion topiccontinuous field of C*-algebras
- Category Latest Changes
- Started by Urs
- Comments 3
- Last comment by Urs
- Last Active Jan 14th 2024

brief note on

*continuous field of C*-algebras*

- Discussion Type
- discussion topicSimon Wassermann
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 14th 2024

- Discussion Type
- discussion topicEberhard Kirchberg
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 14th 2024

- Discussion Type
- discussion topicGelfand-Naimark-Segal construction
- Category Latest Changes
- Started by Urs
- Comments 6
- Last comment by Urs
- Last Active Jan 14th 2024

- Discussion Type
- discussion topicCauchy–Schwarz inequality
- Category Latest Changes
- Started by Dmitri Pavlov
- Comments 4
- Last comment by Urs
- Last Active Jan 14th 2024

- Discussion Type
- discussion topicsigned graph
- Category Latest Changes
- Started by Zaslav
- Comments 2
- Last comment by Urs
- Last Active Jan 14th 2024

- Discussion Type
- discussion topicchromatic homotopy theory
- Category Latest Changes
- Started by Urs
- Comments 10
- Last comment by Urs
- Last Active Jan 14th 2024

I gave

*chromatic homotopy theory*an Idea-section.To be expanded eventually…

- Discussion Type
- discussion topicConway's game of life
- Category Latest Changes
- Started by Urs
- Comments 2
- Last comment by Urs
- Last Active Jan 14th 2024

Stub entry, for the moment just to have a ace for recording this result:

Nico Brown, Carson Cheng, Tanner Jacobi, Maia Karpovich, Matthias Merzenich, David Raucci, Mitchell Riley,

*Conway’s Game of Life is Omniperiodic*[arXiv:2312.02799]The Physics arXiv Blog,

*Mathematicians Prove the “Omniperiodicity” of Conway’s Game of Life*(Dec 2024)

- Discussion Type
- discussion topicepistemology
- Category Latest Changes
- Started by nLab edit announcer
- Comments 10
- Last comment by varkor
- Last Active Jan 13th 2024

- Discussion Type
- discussion topicW-star category > history
- Category Latest Changes
- Started by Urs
- Comments 3
- Last comment by Urs
- Last Active Jan 13th 2024

- Discussion Type
- discussion topicAbraham Westerbaan
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 13th 2024

- Discussion Type
- discussion topicKenta Cho
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 13th 2024

- Discussion Type
- discussion topicquantum lambda-calculus
- Category Latest Changes
- Started by Urs
- Comments 5
- Last comment by Urs
- Last Active Jan 13th 2024

- Discussion Type
- discussion topicNik Weaver
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 13th 2024

- Discussion Type
- discussion topicquantum relation
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 13th 2024

creating a bare minimum, for the moment only to give a home to these references:

Nik Weaver,

*Quantum relations*[arXiv:1005.0354]Nik Weaver, Greg Kuperberg,

*A von Neumann Algebra Approach to Quantum Metrics/Quantum Relations*, Memoirs of the AMS**215**(2011) [ams:memo-215-1010]

- Discussion Type
- discussion topicquantization
- Category Latest Changes
- Started by Urs
- Comments 2
- Last comment by Urs
- Last Active Jan 13th 2024

for when the editing functionality is back, this here is a good textbook to record at

*quantization*:- Nik Weaver,
*Mathematical Quantization*, Chapman and Hall/CRC 2001 (ISBN:9781584880011)

- Nik Weaver,

- Discussion Type
- discussion topicalgebroid
- Category Latest Changes
- Started by J-B Vienney
- Comments 2
- Last comment by Evan Patterson
- Last Active Jan 13th 2024

- Discussion Type
- discussion topicdiamond lemma
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 13th 2024

a stub entry, to make the link work which had long been requested at

*George Bergman*

- Discussion Type
- discussion topicsalamander lemma
- Category Latest Changes
- Started by Todd_Trimble
- Comments 43
- Last comment by Urs
- Last Active Jan 12th 2024

Under definition 1 of salamander lemma, I fixed a mistake in the definition of $A_\Box$ where there was a direct sum of two submodules, where there needed to be a sum (i.e., join) instead.

- Discussion Type
- discussion topictype telescope
- Category Latest Changes
- Started by nLab edit announcer
- Comments 11
- Last comment by nLab edit announcer
- Last Active Jan 12th 2024

- Discussion Type
- discussion topictransition system
- Category Latest Changes
- Started by nLab edit announcer
- Comments 5
- Last comment by Victor Sannier
- Last Active Jan 12th 2024

- Discussion Type
- discussion topicPelle Steffens
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 12th 2024

- Discussion Type
- discussion topicderived smooth manifold
- Category Latest Changes
- Started by Urs
- Comments 4
- Last comment by Urs
- Last Active Jan 12th 2024

am starting to work on derived smooth manifold, so far just a little bit on the motivation (correction of limits of manifolds)

I am a bit hesitant to add a lot of details from David Spivak’s article, since it seems evident that there is some room to streamline the constructions. I need to think about how to deal with this. One really wants to just specify the site as a geometry (for structured (infinity,1)-toposes) and then just say that a derived manifold is a derived scheme in the sense descrived at generalized scheme on this.

In section 10.1 David Spivak discusses one reason that prevented him from setting things up this way: actually I think this points to the following general issue with the definition of geometry (for structured (infinity,1)-toposes): instead of a Grothendieck topology generated by admissible morphisms the definition ought to just refer to a

*coverage*by admissible morphisms, and instead of the stability under pullback one ought to just consider the coverage-style stability condition.More later.

- Discussion Type
- discussion topiclocal section
- Category Latest Changes
- Started by nLab edit announcer
- Comments 1
- Last comment by nLab edit announcer
- Last Active Jan 12th 2024

- Discussion Type
- discussion topicKaluza-Klein mechanism
- Category Latest Changes
- Started by Urs
- Comments 28
- Last comment by Urs
- Last Active Jan 12th 2024

recently there were some questions about it here on the nForum: now there is an entry on the Kaluza-Klein mechanism

- Discussion Type
- discussion topiccomparison lemma
- Category Latest Changes
- Started by nLab edit announcer
- Comments 2
- Last comment by Dmitri Pavlov
- Last Active Jan 11th 2024

- Discussion Type
- discussion topicexceptional field theory
- Category Latest Changes
- Started by Urs
- Comments 7
- Last comment by Urs
- Last Active Jan 11th 2024

started some minimum at

*exceptional field theory*(the formulation of 11d supergravity that makes the exceptional U-duality symmetry manifest)

- Discussion Type
- discussion topicMario Garcia-Fernandez
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 11th 2024

- Discussion Type
- discussion topicstring algebroid
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 11th 2024

- Discussion Type
- discussion topicDominik Rist
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 11th 2024

- Discussion Type
- discussion topicJiří Nárožný
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 11th 2024

- Discussion Type
- discussion topicMehran Jalali Farahani
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 11th 2024

- Discussion Type
- discussion topicstring phenomenology
- Category Latest Changes
- Started by Urs
- Comments 21
- Last comment by Urs
- Last Active Jan 11th 2024

I ended up collecting some references at

*string phenomenology*and accompanying them with a bit of text

- Discussion Type
- discussion topicnonabelian differential cohomology
- Category Latest Changes
- Started by Dmitri Pavlov
- Comments 5
- Last comment by Urs
- Last Active Jan 11th 2024

Created:

## Idea

[…]

## Related concepts

## References

Urs Schreiber,

*On nonabelian differential cohomology*, March 17, 2008, Slides.Domenico Fiorenza, Urs Schreiber, Jim Stasheff,

*Čech cocycles for differential characteristic classes*, Advances in Theoretical and Mathematical Physics 16:1 (2012), 149–250, arXiv:1011.4735, doi:10.1007/BF02104916.

- Discussion Type
- discussion topiccomprehensive factorization system
- Category Latest Changes
- Started by Joshua Meyers
- Comments 24
- Last comment by ncfavier
- Last Active Jan 10th 2024

Linked to from https://ncatlab.org/nlab/show/orthogonal+factorization+system and https://ncatlab.org/nlab/show/final+functor

Todo: add more proofs of this result.

For some reason the xymatrixes were causing errors so I had to comment them out to submit. Here is an example error:

An error occurred when running pdflatex on the following diagram. \xymatrix@=5em{e \ar[r]^\gamma \ar[dr]_{\gamma’} & GFc \ar[d]^{Gf} \ & GFc’} The error was: Timed out

How can I fix this?

- Discussion Type
- discussion topicHypothesis H
- Category Latest Changes
- Started by nLab edit announcer
- Comments 20
- Last comment by Urs
- Last Active Jan 10th 2024

- Discussion Type
- discussion topicMealy morphism
- Category Latest Changes
- Started by nLab edit announcer
- Comments 12
- Last comment by varkor
- Last Active Jan 10th 2024

- Discussion Type
- discussion topicNS5-brane
- Category Latest Changes
- Started by Urs
- Comments 9
- Last comment by Urs
- Last Active Jan 10th 2024

Added a section with a collection of references on intersection laws for black D-branes ending on black NS5-branes. Then I spelled out the case of D6-branes in some detail, collecting the relevant diagrams from the reference EGKRS00, and used this to identify the corresponding M-theory lift by the M5-brane near horizon ADE-orbifolds of the 4-sphere.

- Discussion Type
- discussion topicsemi-metal
- Category Latest Changes
- Started by Urs
- Comments 7
- Last comment by Urs
- Last Active Jan 10th 2024

- Discussion Type
- discussion topicsemi-topological 4d Chern-Simons theory
- Category Latest Changes
- Started by Urs
- Comments 12
- Last comment by Urs
- Last Active Jan 10th 2024

- Discussion Type
- discussion topicMichael Ratz
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 10th 2024

- Discussion Type
- discussion topicSaul Ramos-Sanchez
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active Jan 9th 2024