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arXiv · 2211.12866

A birational involution

Pietro Beri·Laurent Manivel
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Abstract

Given a general K3 surface S of degree 18, lattice theoretic considerations allow to predict the existence of an anti-symplectic birational involution $ϕ$ of the Hilbert cube $S^{[3]}$. We describe this involution in terms of the Mukai model of $S$, with the help of the famous transitive action of the exceptional group $G_2(R)$ on the six-dimensional sphere. We make a connection with Homological Projective Duality by showing that the indeterminacy locus of the involution is birational to a $P^2$-bundle over the dual K3 surface of degree two. We deduce that $ϕ$ is an instance of a Mukai flop.

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Pietro Beri, Laurent Manivel. 2025-09-17. A birational involution. https://arxiv.org/abs/2211.12866

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