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Explicit construction of decomposable Jacobians

  • Mesut Buğday and Mohammad Sadek EMAIL logo
Published/Copyright: May 15, 2025
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Abstract

In this note we give explicit constructions of decomposable hyperelliptic Jacobian varieties over fields of characteristic 0. These include hyperelliptic Jacobian varieties that are isogenous to a product of two absolutely simple hyperelliptic Jacobian varieties, a square of a hyperelliptic Jacobian variety, and a product of four hyperelliptic Jacobian varieties three of which are of the same dimension. As an application, we produce families of hyperelliptic curves with infinitely many quadratic twists having at least two rational non-Weierstrass points, and families of quadruples of hyperelliptic curves together with infinitely many non-square d such that the quadratic twists of each of the curves by d possess at least one rational non-Weierstrass point.

MSC 2010: 14H40; 14H25; 11G30

Funding statement: This work is supported by The Scientific and Technological Research Council of Turkey, TÜBİTAK, research grant ARDEB 1001/122F312. M. Sadek acknowledges the support of the BAGEP Award of the Science Academy, Turkey.

Acknowledgements

The authors would like to thank the anonymous referee for many suggestions that improved the manuscript. These suggestions include the statement and proof of Theorem 3.3.

  1. Communicated by: I. Coskun

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Received: 2024-06-17
Revised: 2024-10-12
Published Online: 2025-05-15
Published in Print: 2025-04-28

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