# 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.

• added a line on $Pin_\pm(n)$, and added pointer to the example of Pin(2)

• Created Nagata-Smirnov metrization theorem .

• started an entry F-theory (the string-theoretic notion)

• I added some more material and references to separable space. Partly this was just to record a MO discussion which would otherwise get eventually buried under centuries of MO sediment, but I’ve included some other things as well. (E.g., I wasn’t aware until now that a product of continuum many separable spaces was still separable.)

• I think the line between the two types of Kan extension (weak versus pointwise) is drawn at the wrong place. Am I missing something?

• just for completeness, it seems we didn’t have this

• Added to flabby sheaf several characterizations of flabbiness, an external one which, unlike the usual definition, is manifestly local, and several internal ones.

• while I am at it…

• This is not a composition between functors but a composition between applications of the functors

• tried to bring the entry Lie group a bit into shape: added plenty of sections and cross links to other nLab material. But there is still much that deserves to be done.

• added to equivariant K-theory comments on the relation to the operator K-theory of crossed product algebras and to the ordinary K-theory of homotopy quotient spaces (Borel constructions). Also added a bunch of references.

(Also finally added references to Green and Julg at Green-Julg theorem).

This all deserves to be prettified further, but I have to quit now.

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

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

• added a sentence to this otherwise empty entry. But it remains a stub

• I have tried to start a table at maximal compact subgroup listing Lie groups and their max compact subgroups. But once again the table does not want to typeset properly.

Have to run now, will try to fiddle with this later.

• I have created an entry on the quaternionic Hopf fibration and then I have tried to spell out the argument, suggested to me by Charles Rezk on MO, that in $G$-equivariant stable homotopy theory it represents a non-torsion element in

$[\Sigma^\infty_G S^7 , \Sigma^\infty_G S^4]_G \simeq \mathbb{Z} \oplus \cdots$

for $G$ a finite and non-cyclic subgroup of $SO(3)$, and $SO(3)$ acting on the quaternionic Hopf fibration via automorphisms of the quaternions.

I have tried to make a rigorous and self-contained argument here by appeal to Greenlees-May decomposition and to tom Dieck splitting. But check.

• added pointer to

But I was really looking for a solid reference for the basic statement that the maximal compact subgroup of $O(n,n)$ is $O(n) \times O(n)$.

• Added definitions of a topology being regular wrt. another topology and coupled to another topology.

• a table-for-inclusion, in order to cross-link the relevant entries

• brief category:people-entry for hyperlinking references at

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

• a bare minimum, for the moment just so as to record this references:

• {#CadekVanzura93} Martin Čadek, Jiří Vanžura, On the classification of oriented vector bundles over 5-complexes, Czechoslovak Mathematical Journal, Vol. 43 (1993), No. 4, 753–764 (dml:128427)
• some minimum, in order to record references