The constructive inverse Galois problem via Hilbert modular forms: realizing the transitive group 17T7

Fuente: arXiv
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Hauptverfasser: van Bommel, Raymond, Costa, Edgar, Elkies, Noam D., Keller, Timo, Schiavone, Sam, Voight, John
Format: Preprint
Veröffentlicht: 2024
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author van Bommel, Raymond
Costa, Edgar
Elkies, Noam D.
Keller, Timo
Schiavone, Sam
Voight, John
author_facet van Bommel, Raymond
Costa, Edgar
Elkies, Noam D.
Keller, Timo
Schiavone, Sam
Voight, John
contents We show how Hilbert modular forms can be used in the constructive inverse Galois problem over the rationals. In particular, we prove that the transitive permutation group 17T7, isomorphic to a split extension of C_2 by PSL_2(FF_16), is a Galois group over the rationals and exhibit an explicit degree 17 polynomial with this Galois group. The group arises from the field of definition of the 2-torsion on an abelian fourfold with real multiplication defined over a real quadratic field; we find such a fourfold attached to a Hilbert modular form. Building upon work of Dembele, we describe a method for reconstructing a period matrix attached to a Hilbert modular form, and we use it to construct the 2-isogeny polynomial. We also rigorously identify the relevant fourfold as the Jacobian of a genus 4 Shimura curve and compute explicit equations for this curve.
format Preprint
id arxiv_https___arxiv_org_abs_2411_07857
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle The constructive inverse Galois problem via Hilbert modular forms: realizing the transitive group 17T7
van Bommel, Raymond
Costa, Edgar
Elkies, Noam D.
Keller, Timo
Schiavone, Sam
Voight, John
Number Theory
12F12 (Primary) 11F80, 11F41, 14G10 (Secondary)
We show how Hilbert modular forms can be used in the constructive inverse Galois problem over the rationals. In particular, we prove that the transitive permutation group 17T7, isomorphic to a split extension of C_2 by PSL_2(FF_16), is a Galois group over the rationals and exhibit an explicit degree 17 polynomial with this Galois group. The group arises from the field of definition of the 2-torsion on an abelian fourfold with real multiplication defined over a real quadratic field; we find such a fourfold attached to a Hilbert modular form. Building upon work of Dembele, we describe a method for reconstructing a period matrix attached to a Hilbert modular form, and we use it to construct the 2-isogeny polynomial. We also rigorously identify the relevant fourfold as the Jacobian of a genus 4 Shimura curve and compute explicit equations for this curve.
title The constructive inverse Galois problem via Hilbert modular forms: realizing the transitive group 17T7
topic Number Theory
12F12 (Primary) 11F80, 11F41, 14G10 (Secondary)
url https://arxiv.org/abs/2411.07857