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arXiv · 0708.2120

Automorphisms of a polynomial ring which admit reductions of type I

Shigeru Kuroda
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Abstract

Recently, Shestakov-Umirbaev solved Nagata's conjecture on an automorphism of a polynomial ring. To solve the conjecture, they defined notions called reductions of types I--IV for automorphisms of a polynomial ring. An automorphism admitting a reduction of type I was first found by Shestakov-Umirbaev. Using a computer, van den Essen--Makar-Limanov--Willems gave a family of such automorphisms. In this paper, we present a new construction of such automorphisms using locally nilpotent derivations. As a consequence, we discover that there exists an automorphism admitting a reduction of type I which satisfies some degree condition for each possible value.

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Shigeru Kuroda. 2007-09-10. Automorphisms of a polynomial ring which admit reductions of type I. https://arxiv.org/abs/0708.2120

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