399 reputation
17
bio website
location
age
visits member for 3 years, 5 months
seen Oct 10 '12 at 1:53

Dec
2
comment Cohomology of $\mathcal O_X$ for toric varieties
Whoops, I fixed it.
Dec
2
revised Cohomology of $\mathcal O_X$ for toric varieties
whoops
Dec
2
asked Cohomology of $\mathcal O_X$ for toric varieties
Dec
2
comment Cohomological decomposition of tensor sheaves?
Oh wow, I thought $H^m(X, \mathcal O_X)=0$ for all $m>0$!!
Dec
2
accepted Cohomological decomposition of tensor sheaves?
Dec
2
comment Cohomological decomposition of tensor sheaves?
Why is it false for $\mathcal O_X$? The only non-vanishing cohomology is $H^0(X,\mathcal O_X)$, so doesn't the formula hold?
Dec
2
asked Cohomological decomposition of tensor sheaves?
Nov
30
accepted Is a regular sequence ordered?
Nov
29
asked Is a regular sequence ordered?
Nov
17
accepted Quotient spaces and equivariant cohomology
Nov
15
awarded  Teacher
Nov
15
answered Negation of if and only if?
Nov
15
comment Quotient spaces and equivariant cohomology
I'm not very familiar with stacks, or with the details of GIT if $G$ is not a torus, but at least when it is the torus the GIT procedure removes the non-free points from $Y$ before quotienting. $X//G$ is supposed to give a scheme $Y$, and I assume that it is constructed thus to avoid having the quotient be a stack.
Nov
15
revised Quotient spaces and equivariant cohomology
Clarified
Nov
15
asked Quotient spaces and equivariant cohomology
Nov
12
asked Yoga of localization in categories?
Nov
6
awarded  Supporter
Nov
6
accepted Why is stable equivalence necessary in topological K-theory?
Nov
5
comment Why is stable equivalence necessary in topological K-theory?
I think there's something basic I'm missing. Stable equivalence is an equivalence relation on isomorphism classes of bundles. Say $E$ and $F$ are isomorphism classes. Then it appears to me that $E = F$ iff $E + G = F + G$ in K-theory. I suppose my question is, why is stable equivalence not "lies in the same isomorphism class"? In particular, what is an example of two non-isomorphic bundles such that when a trivial bundle is added to them, they become isomorphic?
Nov
4
comment Why is stable equivalence necessary in topological K-theory?
Hi Ryan, thanks for your clarification, but it's still murky for me. I don't see why $E \cong F \not \Leftrightarrow (E \oplus G) \cong (F \oplus G)$