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arXiv · 1712.03838

Quotients by Connected Solvable Groups

Gregor Kemper
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Abstract

This paper introduces the notion of an excellent quotient, which is stronger than a universal geometric quotient. The main result is that for an action of a connected solvable group $G$ on an affine scheme Spec$(R)$ there exists a semi-invariant $f$ such that Spec$(R_f) \to$ Spec$((R_f)^G)$ is an excellent quotient. The paper contains an algorithm for computing $f$ and $(R_f)^G$. If $R$ is a polynomial ring over a field, the algorithm requires no Gröbner basis computations, and it also computes a presentation of $(R_f)^G$. In this case, $(R_f)^G$ is a complete intersection. The existence of an excellent quotient extends to actions on quasi-affine schemes.

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Gregor Kemper. 2017-12-11. Quotients by Connected Solvable Groups. https://arxiv.org/abs/1712.03838

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