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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

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- Discussion Type
- discussion topicHořava-Witten theory
- Category Latest Changes
- Started by Urs
- Comments 15
- Last comment by Urs
- Last Active 1 hour ago

stub for Hořava-Witten theory

- Discussion Type
- discussion topicholographic entanglement entropy
- Category Latest Changes
- Started by Urs
- Comments 13
- Last comment by nLab edit announcer
- Last Active 6 hours ago

created a stub for

*holographic entanglement entropy*in reaction to this MO question.

- Discussion Type
- discussion topicIntroduction to Topology -- 1
- Category Latest Changes
- Started by Urs
- Comments 2
- Last comment by Urs
- Last Active 9 hours ago

- Discussion Type
- discussion topicclosed subspace
- Category Latest Changes
- Started by Todd_Trimble
- Comments 7
- Last comment by Urs
- Last Active 9 hours ago

At closed subspace, I added some material on the 14 operations derivable from closures and complements. For no particularly great reason except that it’s a curiosity I’d never bothered to work through until now.

- Discussion Type
- discussion topicANITA experiment
- Category Latest Changes
- Started by Urs
- Comments 5
- Last comment by Urs
- Last Active 11 hours ago

started some minimum, prodded by the suggestion in today’s replacement

- Bhavesh Chauhan, Subhendra Mohanty,
*A common leptoquark solution of flavor and ANITA anomalies*(arXiv:1812.00919)

that leptoquarks could not only explain the flavour anomalies but also the anomalous events seen last year by the ANITA experiment

- Bhavesh Chauhan, Subhendra Mohanty,

- Discussion Type
- discussion topiccomplex projective 3-space
- Category Latest Changes
- Started by Urs
- Comments 11
- Last comment by DavidRoberts
- Last Active 13 hours ago

for completeness and to satisfy links from

*Calabi-Penrose fibration*

- Discussion Type
- discussion topicEugenio Calabi
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active 13 hours ago

- Discussion Type
- discussion topicCalabi-Penrose fibration
- Category Latest Changes
- Started by Urs
- Comments 22
- Last comment by Urs
- Last Active 13 hours ago

- Discussion Type
- discussion topicKouyemon Iriye
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active 16 hours ago

- Discussion Type
- discussion topiclax-idempotent 2-monad
- Category Latest Changes
- Started by John Baez
- Comments 1
- Last comment by John Baez
- Last Active 16 hours ago

I corrected an apparent typo:

A 2-monad $T$ as above is lax-idempotent if and only if for any $T$-algebra $a \colon T A \to A$ there is a 2-cell $\theta_a \colon 1 \Rightarrow \eta \circ a$

to

A 2-monad $T$ as above is lax-idempotent if and only if for any $T$-algebra $a \colon T A \to A$ there is a 2-cell $\theta_a \colon 1 \Rightarrow \eta_A \circ a$

It might be nice to say $\eta_A$ is the unit of the algebra….

- Discussion Type
- discussion topicAQFT
- Category Latest Changes
- Started by zskoda
- Comments 18
- Last comment by Urs
- Last Active 16 hours ago

I did not change anything, I would not like to do it without Urs’s consent and some opinion. The entry AQFT equates algebraic QFT and axiomatic QFT. In the traditional circle, algebraic quantum field theory meant being based on local nets – local approach of Haag and Araki. This is what the entry now describes. The Weightman axioms are somewhat different, they are based on fields belonging some spaces of distributions, and 30 years ago it was called field axiomatics, unlike the algebraic axiomatics. But these differences are not that important for the main entry on AQFT. What is a bigger drawback is that the third approach to axiomatic QFT if very different and was very strong few decades ago and still has some followers. That is the

**S-matrix axiomatics**which does not believe in physical existence of observables at finite distance, but only in the asymptotic values given by the S-matrix. The first such axiomatics was due Bogoliubov, I think. (Of course he later worked on other approaches, especially on Wightman’s. Both the Wightman’s and Bogoliubov’s formalisms are earlier than the algebraic QFT.)I would like to say that axiomatic QFT has 3 groups of approaches, and especially to distinguish S-matrix axiomatics from the “algebraic QFT”. Is this disputable ?

- Discussion Type
- discussion topicThomas Faulkner
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active 16 hours ago

brief

`category: people`

-entry for hyperlinking references at*holographic entanglement entropy*and(!)*AQFT*

- Discussion Type
- discussion topichomotopy theory
- Category Latest Changes
- Started by Tim_Porter
- Comments 19
- Last comment by Urs
- Last Active 23 hours ago

I have deleted an old out of date query box from homotopy theory.

- Discussion Type
- discussion topicunitary matrix
- Category Latest Changes
- Started by Urs
- Comments 5
- Last comment by Urs
- Last Active 1 day ago

*unitary matrix*. just for completeness

- Discussion Type
- discussion topicPlanck's constant
- Category Latest Changes
- Started by Urs
- Comments 9
- Last comment by TobyBartels
- Last Active 2 days ago

started an entry

*Planck’s constant*with a remark on its meaning from the point of view of geometric quantization (and nothing else, so far).

- Discussion Type
- discussion topicThe Rising Sea
- Category Latest Changes
- Started by Urs
- Comments 9
- Last comment by Tim_Porter
- Last Active 2 days ago

created

*The Rising Sea*to record a reference (once I had found it)

- Discussion Type
- discussion topicD=6 N=(1,0) SCFT
- Category Latest Changes
- Started by Urs
- Comments 4
- Last comment by Urs
- Last Active 2 days ago

- Discussion Type
- discussion topicHiroyuki Shimizu
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active 2 days ago

- Discussion Type
- discussion topicMorgan Opie
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active 3 days ago

brief

`category: people`

-entry for hyperlinking references at*localization of a space*and*modal homotopy type theory*

- Discussion Type
- discussion topicmodal homotopy type theory
- Category Latest Changes
- Started by Urs
- Comments 8
- Last comment by Urs
- Last Active 3 days ago

copied over the homotopy-theoretic references from

*modal type theory*to here.

- Discussion Type
- discussion topiclocalization of a space
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active 3 days ago

added pointer to:

- J. Daniel Christensen, Morgan Opie, Egbert Rijke, Luis Scoccola,
*Localization in Homotopy Type Theory*, Higher Structures, 4(1) (2020), 1-32 (arXiv:1807.04155)

- J. Daniel Christensen, Morgan Opie, Egbert Rijke, Luis Scoccola,

- Discussion Type
- discussion topicflavour anomaly
- Category Latest Changes
- Started by Urs
- Comments 137
- Last comment by Urs
- Last Active 3 days ago

- Discussion Type
- discussion topicdual heterotic string theory
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active 4 days ago

added pointer to

- Kurt Lechner, Mario Tonin,
*World-manifold and target space anomalies in heterotic Green-Schwarz strings and five-branes*, in:*Gauge Theories, Applied Supersymmetry and Quantum Gravity II*, pp. 311-318 (1997) (arXiv:hep-th/9610110, doi:10.1142/9781848160927_0022)

- Kurt Lechner, Mario Tonin,

- Discussion Type
- discussion topicconnected space
- Category Latest Changes
- Started by Todd_Trimble
- Comments 17
- Last comment by nLab edit announcer
- Last Active 4 days ago

I added a bunch of things to connected space: stuff on the path components functor, an example of a countable connected Hausdorff space, and the observation that the quasi-components functor is left adjoint to the discrete space functor $Set \to Top$ (Wikipedia reports that the connected components functor is left adjoint to the discrete space functor, but that’s wrong).

This bit about quasi-components functor had never occurred to me before, although it seems to be true. I’m having difficulty getting much information on this functor. For example, does it preserve finite products? I don’t know, but I doubt it. Does anyone reading this know?

- Discussion Type
- discussion topicDirac charge quantization and generalized differential cohomology
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active 4 days ago

- Discussion Type
- discussion topicSL(2,H)
- Category Latest Changes
- Started by Urs
- Comments 2
- Last comment by Urs
- Last Active 5 days ago

- Discussion Type
- discussion topicDieudonné determinant
- Category Latest Changes
- Started by Urs
- Comments 3
- Last comment by Urs
- Last Active 5 days ago

- Discussion Type
- discussion topicJean Dieudonné
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active 5 days ago

added pointer to the article introducing the

*Dieudonné determinant*under “Selected writings”.Now it looks funny that no other of his references are listed here. Hopefully somebody feels awkward enough about this to go ahead and add something.

- Discussion Type
- discussion topicSpin(5,1)
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active 5 days ago

- Discussion Type
- discussion topicCarlos Batista
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active 5 days ago

brief

`category: people`

-entry for hyperlinking references at*SL(2,H)*and*supersymmetry and division algebras*