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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.
Feb
8
answered Describe invariants using coaction.
Jan
28
answered How to show that a polynomial maps an algebraic set to an algebraic set?
Jan
26
revised the top chern class of the holomorphic tangent bundle is the euler class
edited body
Jan
25
comment the top chern class of the holomorphic tangent bundle is the euler class
@user125763: Not a big problem, I did this in my diplom thesis and this is (almost) a straight copy and paste from the source. Hope it is of any use to you.
Jan
25
revised the top chern class of the holomorphic tangent bundle is the euler class
added 2064 characters in body
Jan
25
comment the top chern class of the holomorphic tangent bundle is the euler class
Dear @user125763: I have proved this once for nonsingular complex projective varieties using a couple of big hammers: Borel-Serre identity, Hirzebruch-Riemann-Roch and Hodge Decomposition. If you want, I can show you how that works. I deal with varieties much more than with manifolds, but in the above case the two notions overlap. Concerning complex conjugation, I unfortunately do not know. This sounds like a basic fact though, if it is true. Have you checked standard literature?
Jan
23
answered the top chern class of the holomorphic tangent bundle is the euler class
Jan
22
comment Let $f: U \rightarrow W$ be a morphism of affine algebraic sets and $f': k[W] \rightarrow k[U]$ be the k-algebra morphism of coordinate rings.
Oh, that's true.