« first day (3428 days earlier)      last day (478 days later) » 

8:45 AM
0
Q: When is a smooth point of a projective, simplicial, toric variety $ X_{\Sigma} $ compatibly $ F $-split?

Schemer1A variety $ X $ is $ F $-split if there exists an $ \mathcal{O}_{X} $-linear map $ \phi: F_{\ast}(\mathcal{O}_{X}) \to \mathcal{O}_{X} $ such that $ \phi \circ F^{\sharp} = \operatorname{id}_{\mathcal{O}_{X}} $. Such a map $ \phi $ is called a splitting. A closed sub-scheme $ Y $ of $ X $ is co...

In mathematics, a Frobenius splitting, introduced by Mehta and Ramanathan (1985), is a splitting of the injective morphism OX→F*OX from a structure sheaf OX of a characteristic p > 0 variety X to its image F*OX under the Frobenius endomorphism F*. Brion & Kumar (2005) give a detailed discussion of Frobenius splittings. A fundamental property of Frobenius-split projective schemes X is that the higher cohomology Hi(X,L) (i > 0) of ample line bundles L vanishes. == References == Brion, Michel; Kumar, Shrawan (2005), Frobenius splitting methods in geometry and representation theory, Progres...
 
 
1 hour later…
9:46 AM
14
A: A single paper everyone should read?

Gil KalaiTwo additional papers in combinatorics (That I managed to find on line) each having a beautiful and simple result. On the Shannon Capacity of a Graph by Laszlo Lovasz The Upper Bound Conjecture and Cohen Macaulay Rings by Richard Stanley

The second link seems to be dead, the updated link is math.mit.edu/~rstan/pubs/pubfiles/27.pdf - I posted a comment instead of editing the answer, so that I do not bump an old post to the frontpage. The same paper can certainly be found in other places, it has DOI: 10.1002/sapm1975542135. — Martin Sleziak 55 secs ago
 
10:01 AM
3
A: Topology on the Unitary Dual

Marc PalmConvergence in the Fell topology is equivalent to convergence of matrix coefficients. In the finite-dimensional case, this is equivalent as $\rho_n(g) v \rightarrow \rho(g)v$. Quote from Vogan (http://dedekind.mit.edu/~dav/iso3.pdf) Suppose then that G is a real reductive Lie group. Write $\...

The link to Vogan: Isolated unitary representations seems to be dead. The new link is math.mit.edu/~dav/iso3.pdf - I posted a comment instead of editing the answer, so that I do not bump an old post to the frontpage. — Martin Sleziak 24 secs ago
 
 
8 hours later…
5:49 PM
@MartinSleziak if you click the link in the first revision, you see it doesn't work either (anymore). But it's definitely something my script should handle better (and perhaps I can even do another search for broken Wikipedia links ...)
 
6:01 PM
My bad. I just removed the "archive" part from your link - and after that the link worked.
I will admit that I did not check the original revision.
I think we have mentioned broken Wikipedia links at some point before.
Something similar here:
6
A: Fixed point theorems

Martin BrandenburgThe Arithmetic fixed point theorem (see also MO/30874) states that if $F$ is a formula in number theory with only one free variable $v$, then there is a sentence $A$ such that number theory can prove $A \Leftrightarrow F_v(\underline{[A]})$. An immediate application is Gödel's Theorem.

Gödel's incompleteness theorems are two theorems of mathematical logic that are concerned with the limits of provability in formal axiomatic theories. These results, published by Kurt Gödel in 1931, are important both in mathematical logic and in the philosophy of mathematics. The theorems are widely, but not universally, interpreted as showing that Hilbert's program to find a complete and consistent set of axioms for all mathematics is impossible. The first incompleteness theorem states that no consistent system of axioms whose theorems can be listed by an effective procedure (i.e., an algorithm...
I guess the discussion I remembered might be here:
Jul 23, 2022 at 9:09, by Martin Sleziak
When I try with SEDE, I get only 144 posts with %2527.
Jul 23, 2022 at 9:11, by Glorfindel
BTW it's better to search with double quotes: https://stackexchange.com/search?q=url%3A%22%252527%22
I have edited the above post before - and I did not notice the problem: mathoverflow.net/posts/127089/revisions
Searching for url:"*wikipedia.org/*%25*" returns 309 posts on MO.
 
 
2 hours later…
7:50 PM
@MartinSleziak I think I got it working.
 

« first day (3428 days earlier)      last day (478 days later) »