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arXiv · 1912.08109

Special groups, versality and the Grothendieck-Serre conjecture

Zinovy Reichstein·Dajano Tossici
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Abstract

Let $k$ be a base field and $G$ be an algebraic group over $k$. J.-P. Serre defined $G$ to be special if every $G$-torsor $T \to X$ is locally trivial in the Zariski topology for every reduced algebraic variety $X$ defined over $k$. In recent papers an a priori weaker condition is used: $G$ is called special if every $G$-torsor $T \to Spec(K)$ is split for every field $K$ containing $k$. We show that these two definitions are equivalent. We also generalize this fact and propose a strengthened version of the Grothendieck-Serre conjecture based on the notion of essential dimension.

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Zinovy Reichstein, Dajano Tossici. 2019-12-17. Special groups, versality and the Grothendieck-Serre conjecture. https://arxiv.org/abs/1912.08109

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