3,494 research outputs found

    Constructing Class invariants

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    Shimura reciprocity law allows us to verify that a modular function is a class invariant. Here we present a new method based on Shimura reciprocity that allows us not only to verify but to find new class invariants from a modular function of level NN.Comment: 12 page

    Automorphisms of Curves and Weierstrass semigroups for Harbater-Katz-Gabber covers

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    We study pp-group Galois covers X→P1X \rightarrow \mathbb{P}^1 with only one fully ramified point. These covers are important because of the Katz-Gabber compactification of Galois actions on complete local rings. The sequence of ramification jumps is related to the Weierstrass semigroup of the global cover at the stabilized point. We determine explicitly the jumps of the ramification filtrations in terms of pole numbers. We give applications for curves with zero pp--rank: we focus on maximal curves and curves that admit a big action. Moreover the Galois module structure of polydifferentials is studied and an application to the tangent space of the deformation functor of curves with automorphisms is given
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