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Endomorphisms of Two Dimensional Jacobians and Related Finite Algebras

Published online by Cambridge University Press:  20 November 2018

William Butske*
Affiliation:
Department of Mathematics, Rose-Hulman Institute of Technology, Terre Haute, IN 47907, U.S.A. e-mail: [email protected]
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Abstract

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Zarhin proves that if $C$ is the curve ${{y}^{2}}\,=\,f(x)$ where $\text{Ga}{{\text{l}}_{\mathbb{Q}}}(f(x))\,=\,{{S}_{n}}$ or ${{A}_{n}}$, then $\text{En}{{\text{d}}_{\overline{\mathbb{Q}}}}(J)\,=\,\mathbb{Z}$. In seeking to examine his result in the genus $g\,=\,2$ case supposing other Galois groups, we calculate $\text{En}{{\text{d}}_{\overline{\mathbb{Q}}}}(J)\,{{\otimes }_{\mathbb{Z}}}\,{{\mathbb{F}}_{2}}$ for a genus 2 curve where $f(x)$ is irreducible. In particular, we show that unless the Galois group is ${{S}_{5}}$ or ${{A}_{5}}$, the Galois group does not determine $\text{En}{{\text{d}}_{\overline{\mathbb{Q}}}}(J)$.

Keywords

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 2012

References

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