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awarded  Yearling 
Jul 2 
awarded  Curious 
Oct 23 
awarded  Yearling 
Apr 11 
awarded  Nice Question 
Mar 12 
comment 
What are some triangulations of Grassmannians?
I have nothing against Schubert cells, but the attaching maps are very complicated. I would be just as interested in hearing about a regular cell complex structure as a triangulation, but it's easy to get from one to the other so I asked about triangulations. If you know a triangulation that refines the Schubert stratification, so much the better! 
Mar 12 
asked  What are some triangulations of Grassmannians? 
Nov 16 
awarded  Popular Question 
Oct 23 
awarded  Yearling 
Oct 13 
comment 
The highest root of an ADE quiver
I was a little off: a nontrivial irrep matches to O(1) on a reduced P^1. The trivial irrep matches to the structure sheaf of the schemetheoretic exceptional fiber, shifted by 1. More stuff like this available here arxiv.org/abs/math/9812016 
Oct 12 
comment 
The highest root of an ADE quiver
There's an equivalence of derived categories (Gequivariant coherent sheaves on C^2) = (coherent sheaves on a minimal resolution of the Duval singularity). It sends a nontrivial irrep of G (supported at the origin in C^2) to the structure sheaf of a component of the exceptional fiber. I wonder which sheaf on C^2 corresponds to a skyscraper on a node in the exceptional fiber. Whatever it is it has maps to and from the irrep. 
Sep 26 
answered  When is the derived category of representations of a finite poset equivalent to its opposite? 
Nov 17 
comment 
When are the fibers of a resolution of singularities reduced?
The usual resolutions of the D_n, E_6, E_7, and E_8 surface singularities do not have reduced fibers. The multiplicity of a component is the coefficient in the maximal root of the corresponding simple root. 
Oct 24 
awarded  Yearling 
Oct 10 
awarded  Popular Question 
Jul 1 
asked  Is endoscopy interesting in simplylaced cases? 
May 27 
awarded  Nice Answer 
Nov 18 
accepted  How often does suspension define an action of Z/2 on a category of module spectra? 
Nov 17 
asked  How often does suspension define an action of Z/2 on a category of module spectra? 
Oct 28 
comment 
What are some open problems in toric varieties?
Let $X$ be a complete toric variety, necessarily neither smooth nor projective. Is there a nontrivial vector bundle on $X$? Payne has constructed examples that have no one or twodimensional bundles, and constructing vector bundles of higher rank on these is still open. The "mirror" question is whether there exists a Lagrangian submanifold of $(\mathbb{C}^*)^n$ satisfying certain asymptotic conditions coming from the fan of $X$. 
Oct 26 
comment 
Sheaves without global sections
But the condition that Frob is an isomorphism on H^i(X,O) is much weaker than being Frobenius split, like Torsten's example of a generic hypersurface. By now, does the opposite question look more interesting? On which varieties does every vector bundle have cohomology? 