Reputation
5,418
Next privilege 10,000 Rep.
Access moderator tools
Badges
1 12 41
Newest
 Nice Answer
Impact
~62k people reached

Mar
4
awarded  Electorate
Mar
4
answered Isomorphism between End$(V)\otimes A$ and End$_A(V\otimes A)$.
Mar
3
comment Can a birational morphism surject from an affine to a projective variety?
@Ben: I am not so much interested in pathologic cases, you may safely assume that all the objects are actually interesting.
Mar
3
asked Can a birational morphism surject from an affine to a projective variety?
Mar
3
asked Resolution of singularities of the determinant hypersurface
Mar
1
answered Orbits of algebraic groups (dimension of connected components)
Feb
27
comment Is this graph theory problem NP-Complete?
What I ment to say is: I expect the answer to be a resounding "we still don't know", all we know that it is in P.
Feb
27
comment Is this graph theory problem NP-Complete?
Technical nag: Your problem is not a decision problem, so it would at best be NP-hard. However, you can do DFS from each vertex to find all cycles in which that vertex is contained. This sounds like polynomial time to me, and if you can prove that the problem is not NP-hard, then you would have shown P$\ne$NP.
Feb
27
comment Qing Liu's definition of an algebraic variety, a non-separated line
This is a big problem with the notion of "variety" that has bugged me for quite some time as well: There is no really good consensus about what the word precisely means.
Feb
19
answered Covers with fixed ramification
Feb
19
awarded  Nice Question
Feb
18
comment Covers with fixed ramification
From your notation I take it that $D$ is an effective (Weyl) divisor? In other words, a codimension one subvariety? Because the multiplicities of that divisor are quite meaningless for the ramification question at hand. Also. Is $D$ base point free by any chance?
Feb
16
answered Which rational functions $\mathbb{P}^1\rightarrow k$ are regular at the point at infinity?
Feb
10
awarded  Nice Question
Feb
9
awarded  Enlightened
Feb
9
comment How many non-increasing sequences are there over the natural numbers?
@dtldarek: Very true - the mental image was, of course, that this is so-to-speak the "limit point" of the sequence.
Feb
9
awarded  Nice Answer
Feb
9
answered How many non-increasing sequences are there over the natural numbers?
Feb
9
revised Describe invariants using coaction.
added 273 characters in body
Feb
9
comment Describe invariants using coaction.
@LJR - yes, indeed, I forgot to elaborate on that. Except maybe you should write $c_i$ instead of $c$, because you could have $\alpha_i(1)\ne\alpha_j(1)$. Doesn't affect the proof though.