π₁ of Miranda moduli spaces of elliptic surfaces

Abstract

We give finite presentations for the fundamental group of moduli spaces due to Miranda of smooth Weierstrass curves over [Formula: see text] which extend the classical result for elliptic curves to the relative situation over the projective line. We thus get natural generalisations of [Formula: see text] presented in terms of [Formula: see text] , [Formula: see text] on one hand and the first examples of fundamental groups of moduli stacks of elliptic surfaces on the other. Our approach exploits the natural [Formula: see text] -action on Weierstrass curves and the identification of [Formula: see text] -fixed loci with smooth hypersurfaces in an appropriate linear system on a projective line bundle over [Formula: see text] . The fundamental group of the corresponding discriminant complement can be presented in terms of finitely many generators and relations using methods in the Zariski tradition

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