On the birational section conjecture with local conditions

Jakob Stix

doi:10.1007/s00222-014-0514-3

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arXiv · 1203.3236

On the birational section conjecture with local conditions

Jakob Stix

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Abstract

A birationally liftable Galois section s of a hyperbolic curve X/k over a number field k yields an adelic point x(s) in the smooth completion of X. We show that x(s) is X-integral outside a set of places of Dirichlet density 0, or s is cuspidal. The proof relies on $GL_2(F_\ell)$-quotients of $π_1(U)$ for some open U of X. If k is totally real or imaginary quadratic, we prove that all birationally adelic, non-cuspidal Galois sections come from rational points as predicted by the section conjecture of anabelian geometry. As an aside we also obtain a strong approximation result for rational points on hyperbolic curves over Q or imaginary quadratic fields.

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Jakob Stix. 2015-09-17. On the birational section conjecture with local conditions. https://doi.org/10.1007/s00222-014-0514-3

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