1,503 reputation
614
bio website
location
age
visits member for 5 years
seen Oct 7 at 17:52

1d
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 scheme-theoretic 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 (G-equivariant 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 simply-laced 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 two-dimensional 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?