# Jesko Hüttenhain

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bio website nullteilerfrei.de location Germany age 28 member for 2 years, 9 months seen 14 hours ago profile views 636

I'm a PhD student with research interests in Algebraic Geometry, Algebraic Complexity Theory and Geometric Invariant Theory.

# 581 Actions

 Feb27 accepted Does the quotient of an algebraic group by its neutral component always split? Feb27 asked Does the quotient of an algebraic group by its neutral component always split? Feb25 reviewed Approve suggested edit on Probability Distribution Function for Nonlinear Function Feb25 reviewed Approve suggested edit on Compare the topological spaces? Feb24 answered Dimension of a $G$-variety $X$ that is a finite union of $G$-orbits Feb23 reviewed Approve suggested edit on For what values of $k$ does this system of equations have a unique solution? Feb23 reviewed Approve suggested edit on Representing $-2.5$ as a floating point number Feb21 accepted Confusion about the quotient $G/B$ Feb21 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. Feb21 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. Feb21 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 $U$. Feb21 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? Feb21 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. Feb21 asked Confusion about the quotient $G/B$ Feb18 awarded algebraic-geometry Feb16 answered Prove that ${n^5 - n}$ is divisible by 5 Feb16 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? Feb15 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. Feb14 revised Degree of blow up of a smooth projective surface added 16 characters in body Feb14 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.