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bio website nullteilerfrei.de
location Germany
age 29
visits member for 3 years, 1 month
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I'm a PhD student with research interests in Algebraic Geometry, Algebraic Complexity Theory and Geometric Invariant Theory.


Feb
23
reviewed Approve suggested edit on Representing $-2.5$ as a floating point number
Feb
21
accepted Confusion about the quotient $G/B$
Feb
21
comment Confusion about the quotient $G/B$
Alright. A categorical quotient is defined on wikipedia, and I think the problem is that $\operatorname{Spec}(\C[G]^U)$ is a categorical quotient inside the category of affine varieties, but it is not a categorical quotient in the category of varieties, or even $\C$-schemes.
Feb
21
comment Confusion about the quotient $G/B$
Okay. I think this will help me to get there. @TobiasKildetoft: You were right, the flaw is in my argument that a quotient is affine just because it has a finitely generated ring of rational functions.
Feb
21
comment Confusion about the quotient $G/B$
Hm. I see what you are saying. My line of argument, however, is more like this: I can consider $\operatorname{Spec}(\C[G]^U)$ which is an affine variety. It also seems to be a categorical quotient of $G$ by $U$.
Feb
21
comment Confusion about the quotient $G/B$
But we are talking about affine varieties, and for those kinds of schemes it's true. Just to be clear, though: You say that $G/U$ is not affine, right?
Feb
21
comment Confusion about the quotient $G/B$
I thought that I could take the spectrum of this finitely generated algebra and get an affine, categorical quotient: Since those are unique and geometric quotients are categorical, the statement would follow.
Feb
21
asked Confusion about the quotient $G/B$
Feb
18
awarded  algebraic-geometry
Feb
16
answered Prove that ${n^5 - n}$ is divisible by 5
Feb
16
reviewed Approve suggested edit on Why is a sequence $(x_1, x_2, x_3,…)$ eventually periodic if the set $\{x_1, x_2, x_3,…\}$ is finite?
Feb
15
comment When does one need $k$ to be algebraically closed to compute the (co)tangent space with the Jacobian?
I just wanted to remark that the Hilbert Nullstellensatz only yields that all maximal ideals are of the form $(x_1-a_1,\ldots,x_n-a_n)$ over an algebraically closed field. Maybe that is the source of the problem, at least in the case where you need to go from the origin to any point.
Feb
14
revised Degree of blow up of a smooth projective surface
added 16 characters in body
Feb
14
comment Degree of blow up of a smooth projective surface
@AsalBeagDubh: I will do that then. I did not want to discourage people from giving a more detailed answer.
Feb
14
comment Degree of blow up of a smooth projective surface
I had a similar question once, and at least part of your first question is addressed in this paper.
Feb
14
answered Degree of blow up of a smooth projective surface
Feb
6
answered Torus orbit closures and rank-1 subtori
Feb
2
reviewed Approve suggested edit on Perturbation Sums Question
Feb
2
reviewed Approve suggested edit on When the derivative of a polynomial is 0 (Dummit & Foote, Page 548)
Feb
2
reviewed Approve suggested edit on If $K$ is not perfect then there are inseparable irreducible polynomials (Dummit & Foote, P549 )