A universal Torelli theorem for elliptic surfaces

C. S. Rajan; S. Subramanian

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arXiv · 1706.00564

A universal Torelli theorem for elliptic surfaces

C. S. Rajan·S. Subramanian

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Abstract

Given two semistable, non potentially isotrivial elliptic surfaces over a curve $C$ defined over a field of characteristic zero or finitely generated over its prime field, we show that any compatible family of effective isometries of the N{\'e}ron-Severi lattices of the base changed elliptic surfaces for all finite separable maps $B\to C$ arises from an isomorphism of the elliptic surfaces. Without the effectivity hypothesis, we show that the two elliptic surfaces are isomorphic. We also determine the group of universal automorphisms of a semistable elliptic surface. In particular, this includes showing that the Picard-Lefschetz transformations corresponding to an irreducible component of a singular fibre, can be extended as universal isometries. In the process, we get a family of homomorphisms of the affine Weyl group associated to $\tilde{A}_{n-1}$ to that of $\tilde{A}_{dn-1}$, indexed by natural numbers $d$, which are closed under composition.

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C. S. Rajan, S. Subramanian. 2017-06-02. A universal Torelli theorem for elliptic surfaces. https://arxiv.org/abs/1706.00564

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