17,619 reputation
14492
bio website math.purdue.edu/~dvb
location
age
visits member for 5 years, 6 months
seen 6 hours ago

12h
comment Commuting diagram, algebraic cycles and K-theory
$ch(A\boxtimes B) = ch(p^*A\otimes q^*B)= p^*ch(A)\cdot q^*ch(B) = ch(A)\times ch(B)$, where $p,q$ denote projections on $X\times Y$, and I'm using naturality and the fact that $ch$ is homomorphism (unless that was your question).
Aug
23
revised Vanishing of sheaf cohomology with compact support
added 3 characters in body
Aug
22
revised Vanishing of sheaf cohomology with compact support
added 45 characters in body
Aug
22
comment Vanishing of sheaf cohomology with compact support
Igor, thanks. I'll edit.
Aug
22
answered Vanishing of sheaf cohomology with compact support
Aug
15
comment Motivic fundamental group of the moduli space of curves?
Will, no I would agree that these examples aren't exotic. The pure graded part of the moduli of semistable bundles come from $Sp_{2g}$ as you surmised.
Aug
14
comment Motivic fundamental group of the moduli space of curves?
Actually, I think that the reductive part of $\pi_1^{mot}(M_g)$ would bigger than $Sp_{2g}$. You can see my answer to mathoverflow.net/questions/186133/… for why I think so.
Aug
12
comment nonsingular schemes and regularity of stalks
I didn't down vote you, but I do have to ask, what is your definition of nonsingular? Often nonsingular=regular by definition.
Aug
7
answered When $mB \neq B$? $m$ is a maximal ideal of $A$, $A \subseteq B$
Jul
29
awarded  Good Answer
Jul
29
comment Genus of a plane curve of the form $\prod_{i=1}^n (a_iX+b_iY+Z) = Z^n$
It depends on whether genus means arithmetic or geometric genus. Of course, you and probably the OP mean the latter.
Jul
28
awarded  Nice Answer
Jul
27
awarded  Nice Answer
Jul
26
comment Relationship between étale and topological $K(\pi,1)$s
Yes, I believe 2 and 3 are still open. Serre, in one of his books, asked explicitly whether the Higman group occurs as the fundamental group of a smooth projective variety. If so, it would provide a counterexample to 2. I'm not aware of any progress on this.
Jul
26
comment Relationship between étale and topological $K(\pi,1)$s
It's kind of a shame that the name "good group" seems to have stuck. Given the large community of mathematicians here, I wonder if can vote to change it to something more else. How about "Serre group"?
Jul
26
revised Relationship between étale and topological $K(\pi,1)$s
added 323 characters in body
Jul
26
comment Relationship between étale and topological $K(\pi,1)$s
The point of going to level $\ge 3$ is that $\Gamma(n)$ acts without fixed points, so you can use the usual $\pi_1$.
Jul
25
answered Relationship between étale and topological $K(\pi,1)$s
Jul
25
comment Relationship between étale and topological $K(\pi,1)$s
I strongly suspect that the main question is false, but I'll need to think more about it. There is a typo in 2 by the way. 2 and 3 are open as far as I know. Although there exists smooth projective varieties with non residually finite fundamental groups (Toledo,...).
Jul
24
revised Intuition behind the Kodaira Vanishing Theorem?
added 361 characters in body