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- Discussion Type
- discussion topicstring scattering amplitude
- Category Latest Changes
- Started by Urs
- Comments 3
- Last comment by Urs
- Last Active 2 hours ago

added a bunch of pointers to the literature (with brief comments) at

*string scattering amplitude*.Also added a corresponding paragraph at

*effective field theory*.(this is still in reaction to that MO discussion, specifically to the question here)

- Discussion Type
- discussion topicenhanced gauge symmetry
- Category Latest Changes
- Started by Urs
- Comments 2
- Last comment by Urs
- Last Active 4 hours ago

- Discussion Type
- discussion topicTaejin Lee
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active 4 hours ago

brief category:people-entry for hyperlinking references at

*string field theory*,*gauge enhancement*,*BFSS matrix model*and*IKKT matrix model*.

- Discussion Type
- discussion topicDirac-Born-Infeld action
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active 9 hours ago

added pointer to Schwarz 01

- Discussion Type
- discussion topicgeneralized the
- Category Latest Changes
- Started by David_Corfield
- Comments 66
- Last comment by Richard Williamson
- Last Active 13 hours ago

I added the HoTT introduction rule for ’the’, then added a speculative remark on why say things like

The Duck-billed Platypus is a primitive mammal that lives in Australia.

- Discussion Type
- discussion topicQuantale
- Category Latest Changes
- Started by David_Corfield
- Comments 11
- Last comment by pcapriotti
- Last Active 1 day ago

- Added Todd's definition of *-quantale to quantale. Is there anything about enrichment in such things that's worth adding?

- Discussion Type
- discussion topicmodel structures on dg-categories
- Category Latest Changes
- Started by nLab edit announcer
- Comments 1
- Last comment by nLab edit announcer
- Last Active 2 days ago

- Discussion Type
- discussion topiccogerm differential form
- Category Latest Changes
- Started by TobyBartels
- Comments 1
- Last comment by TobyBartels
- Last Active 2 days ago

- Discussion Type
- discussion topicKripke-Joyal semantics
- Category Latest Changes
- Started by David_Corfield
- Comments 1
- Last comment by David_Corfield
- Last Active 2 days ago

- Discussion Type
- discussion topicabsolute differential form
- Category Latest Changes
- Started by TobyBartels
- Comments 1
- Last comment by TobyBartels
- Last Active 2 days ago

- Discussion Type
- discussion topicelementary (infinity,1)-topos
- Category Latest Changes
- Started by David_Corfield
- Comments 11
- Last comment by Mike Shulman
- Last Active 2 days ago

I added the reference

- Nima Rasekh,
*A Theory of Elementary Higher Toposes*, (arXiv:1805.03805)

- Nima Rasekh,

- Discussion Type
- discussion topicWeiss topology and Goodwillie calculus
- Category Latest Changes
- Started by Urs
- Comments 48
- Last comment by Tim Campion
- Last Active 4 days ago

created an extemely stubby stub

*Weiss topology*, just to record pointer to that cool fact which Dmitri Pavlov advertised on MO (here).I have no time to expand on the entry right now. But maybe somebody else here does? Would be worthwhile.

- Discussion Type
- discussion topicTwelf
- Category Latest Changes
- Started by Mike Shulman
- Comments 1
- Last comment by Mike Shulman
- Last Active 4 days ago

- Discussion Type
- discussion topicgeneralized Reedy model structure
- Category Latest Changes
- Started by Urs
- Comments 8
- Last comment by Urs
- Last Active 5 days ago

I have added some first content to

*generalized Reedy model structure*.

- Discussion Type
- discussion topicReedy model structure
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active 5 days ago

- Discussion Type
- discussion topicregular monomorphism in an (oo,1)-category
- Category Latest Changes
- Started by Urs
- Comments 33
- Last comment by Tim Campion
- Last Active 5 days ago

I split off an entry regular monomorphism in an (infinity,1)-category from regular monomorphism. But not much there yet.

- Discussion Type
- discussion topicaxion
- Category Latest Changes
- Started by Urs
- Comments 6
- Last comment by Urs
- Last Active 5 days ago

added to

*axion*a pointer to this recent article:Joseph P. Conlon, M.C. David Marsh,

*Searching for a 0.1-1 keV Cosmic Axion Background*(arXiv:1305.3603)Primordial decays of string theory moduli at $z \sim 10^{12}$ naturally generate a dark radiation Cosmic Axion Background (CAB) with $0.1 - 1 keV$ energies. This CAB can be detected through axion-photon conversion in astrophysical magnetic fields to give quasi-thermal excesses in the extreme ultraviolet and soft X-ray bands. Substantial and observable luminosities may be generated even for axion-photon couplings $\ll 10^{-11} GeV^{-1}$. We propose that axion-photon conversion may explain the observed excess emission of soft X-rays from galaxy clusters, and may also contribute to the diffuse unresolved cosmic X-ray background. We list a number of correlated predictions of the scenario.

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

brief category:people-entry for hyperlinking of references at

*cobordism ring*,*cohomotpy*and*Pontrjagin-Thom construction*

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

added brief Properties-section

*Relation to cohomotopy*

- Discussion Type
- discussion topiccohomotopy
- Category Latest Changes
- Started by Urs
- Comments 4
- Last comment by Urs
- Last Active 5 days ago

At the old entry

*cohomotopy*used to be a section on how it may be thought of as a special case of non-abelian cohomology. While I (still) think this is an excellent point to highlight, re-reading this old paragraph now made me feel that it was rather clumsily expressed. Therefore I have rewritten (and shortened) it, now the third paragraph of the Idea-section.(We had had long discussion about this entry back in the days, but it must have been before we switched to nForum discussion, because on the nForum there seems to be no trace of it.)

- Discussion Type
- discussion topicBaas-Sullivan theory
- Category Latest Changes
- Started by David_Corfield
- Comments 1
- Last comment by David_Corfield
- Last Active 5 days ago

- Discussion Type
- discussion topicBaas-Sullivan theory
- Category Latest Changes
- Started by David_Corfield
- Comments 1
- Last comment by David_Corfield
- Last Active 5 days ago

Looking back at an old Café thread, I see Neil Strickland telling us about Baas-Sullivan theory.

Various comments:

1) Baas-Sullivan theory allows you to start with a cobordism spectrum R and introduce singularities to construct R-module spectra that can be thought of as R/(x1,…,xn), where xi ∈ π*R.

2) This is computationally tractable when the elements xi form a regular sequence. You can construct connective Morava K-theories from complex cobordism this way, for example. You can also get ordinary homology, as the cobordism theory of complexes that are allowed arbitrary singularities of codimension at least two.

3) The original Baas-Sullivan framework is quite technical, and combinatorially complex. It is now easier to use the framework developed in the book by Elmendorf, Kriz, Mandell and May.

4) This procedure always gives R-modules, so if you start with MU (= complex cobordism) or MSO or MO, you will always end up with something complex orientable. In particular, you cannot get tmf or KO or the sphere spectrum from MU.

5) You can get more things if you do cobordism of manifolds with extra structure, such as a spin bundle or framing, for example. It is probably possible to get kO from MSpin. It might even be possible to get tmf from MString.

6) There is a theorem that I think appears in an old book by Buoncristiano, Rourke and Sanderson, showing that any generalised homology theory is a cobordism theory of manifolds with some kind of extra structure and singularities. I don’t think that they were able to given any nonobvious concrete examples other than ordinary homology, and I don’t think that anyone else has managed to go anywhere with this theory. But perhaps it would be worth taking another look.

Let’s see if any passing expert can help with an entry.

- Discussion Type
- discussion topicYoneda structure
- Category Latest Changes
- Started by Thomas Holder
- Comments 2
- Last comment by Mike Shulman
- Last Active 5 days ago

I started a new page Yoneda structure. For the moment mostly references though hopefully I will supply more content in the coming days.

- Discussion Type
- discussion topictriangle identities
- Category Latest Changes
- Started by Tim_Porter
- Comments 2
- Last comment by Urs
- Last Active 6 days ago

Someone anonymous has noted that the labels in two diagrams in triangle identities are misplaced. This seems clear. As the diagrams are external, can someone edit them who has access to the original code? There seem to be other errors (e.g. a C should be a D), as well.

- Discussion Type
- discussion topicstring network
- Category Latest Changes
- Started by Urs
- Comments 2
- Last comment by Urs
- Last Active 6 days ago

Some minimum, to go along with the entry on membrane triple junctions.

- Discussion Type
- discussion topictriple membrane junction
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active 6 days ago

Started some minimum. This configuration was an early source of speculation of higher structures in M-theory, since it generalizes the binary string junctions between D-branes that carry gauge fields to

*something*trinary.I left a brief remark on that.

But for the moment what I wanted to mainly record is the remark that if one does accept the story of the M-theory lift of gauge enhancement on D6-branes, in terms of M2-branes wrapping 2-spheres that touch along the shape of a Dynkin diagram blowup of an ADE-singularity, then such triple membrane junctions must correspond to blowups of the dihedral ADE-singularities as well as the three exceptional cases, since in these cases the Dynkin diagram has a triple junction node.

- Discussion Type
- discussion topicM-theory lift of gauge enhancement on D6-branes
- Category Latest Changes
- Started by Urs
- Comments 2
- Last comment by Urs
- Last Active 6 days ago

I am making some notes at

*M-theory lift of gauge enhancement on D6-branes*. For the moment I have just extracted directly from- Ashoke Sen,
*A Note on Enhanced Gauge Symmetries in M- and String Theory*, JHEP 9709:001,1997 (arXiv:hep-th/9707123)

Need to interrupt now.

- Ashoke Sen,

- Discussion Type
- discussion topicM-theory on G2-manifolds
- Category Latest Changes
- Started by Urs
- Comments 10
- Last comment by Urs
- Last Active 6 days ago

started

*M-theory on G2-manifolds*

- Discussion Type
- discussion topicADE singularity
- Category Latest Changes
- Started by Urs
- Comments 15
- Last comment by Urs
- Last Active 6 days ago

Yesterday I had added some rough bits and pieces and some references to

*ADE singularity*, and cross-linked with relevant entries such as*ADE classification*and*M-theory on G2-manifolds*. But for the moment this remains a stub.

- Discussion Type
- discussion topicD8-brane
- Category Latest Changes
- Started by Urs
- Comments 1
- Last comment by Urs
- Last Active 7 days ago