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Additive group actions on Danielewski varieties and the Cancellation Problem

Adrien Dubouloz
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Abstract

The cancellation problem asks if two complex algebraic varieties X and Y of the same dimension such that X\times\mathbb{C} and Y\times\mathbb{C} are isomorphic are isomorphic. Iitaka and Fujita established that the answer is positive for a large class of varieties of any dimension. In 1989, Danielewski constructed a famous counter-example using smooth affine surfaces with additive group actions. His construction was further generalized by Fieseler and Wilkens to describe a larger class of affine surfaces. Here we construct higher dimensional analogues of these surfaces. We study algebraic actions of the additive group \mathbb{C}\_{+} on certain of these varieties, and we obtain counter-examples to the cancellation problem in any dimension n\geq2 .

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Adrien Dubouloz. 2005-07-25. Additive group actions on Danielewski varieties and the Cancellation Problem. https://arxiv.org/abs/math/0507505

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