# Start a new discussion

## Not signed in

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

## Site Tag Cloud

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

• I do not understand the entry G-structure. G-structure is, as usual, defined there as the principal $G$-subbundle of the frame bundle which is a $GL(n)$-principal bundle. I guess this makes sense for equivariant injections along any Lie group homomorphism $G\to GL(n)$. The entry says something about spin structure, warning that the group $Spin(n)$ is not a subgroup of $GL(n)$. So what is meant ? The total space of a subbundle is a subspace at least. Does this mean that I consider the frame bundle first as a (non-principal) $Spin(n)$-bundle by pulling back along a fixed noninjective map $Spin(n)\to GL(n)$ and then I restrict to a chosen subspace on which the induced action of Spin group is principal ?

• slightly expanded the Idea-section. But the entry remains a stub

• I was thinking/hoping now that a general approach to perturbative QFT should exist, where all Feynman amplitudes are regarded not as singular distributions on $M^n$, but as smooth differential forms on the FM-compactification of the configuration space of $n$ points. Mentioning this hunch to Igor Khavkine, he immediately recalled having heard Marko Berghoff speak about developing just that in his thesis Berghoff 14.

• keep needing to point to this, so I finally gave it its own entry

• Page created, but author did not leave any comments.

• Created, mainly with stuff from the overview.

• A stub to fulfil a link.

• Page created, but author did not leave any comments.

• Made a start. I linked to lenses (in computer science) since according to the penultimate entry there, Gödel provided the first instance. I guess the connection goes via games, linear logic, etc.

Anyway, to be expanded by someone who knows about these things.

• Heisuke Hironaka, Resolution of Singularities of an Algebraic Variety Over a Field of Characteristic Zero: I, Annals of Mathematics Second Series, Vol. 79, No. 1 (Jan., 1964), pp. 109-203 (95 pages) (jstor:1970486)

• Michael Atiyah, Resolution of singularities and Division of Distributions, Communications in Pure and Applied Mathematics, vol. XXIII, 145-150 (1970)

with some comment

• with heroic effort, I finally discovered the unmatched dollar sign. Now the entry saves again, and hence properly redirects again

• added to combinatorial model category a reference (here) discussing that using a funny set-theoretic assumption about large cardinals, every cofibrantly generated mod cat is Quillen equivalent to a combinatorial one.

Weird that set-theory...

• A stub (now just recording references and links) graph homology with redirect and section open also for graph cohomology. Related person entry Andrey Lazarev and more references at operad. In operadic literature there is a terminology Feynman transform.

• I started an entry on Chern-Simons theory, after having been inspired by news that Witten has thought up a new Morse theory approach to the defining the path integral nonperturbatively (see Not Even Wrong), and Urs' encouragement. There is so much material on Chern-Simons theory, and I am only familiar with a small portion of it, that having to do with "extended topological quantum field theory".
• some pointers