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Computing the Cassels–Tate pairing for genus two jacobians with rational two-torsion points

Published online by Cambridge University Press:  06 December 2024

JIALI YAN*
Affiliation:
University of Cambridge, 28 Howards Lane, SW15 6NQ, London. e-mail:[email protected]

Abstract

In this paper, we give an explicit formula as well as a practical algorithm for computing the Cassels–Tate pairing on $\text{Sel}^{2}(J) \times \text{Sel}^{2}(J)$ where J is the Jacobian variety of a genus two curve under the assumption that all points in J[2] are K-rational. We also give an explicit formula for the Obstruction map $\text{Ob}: H^1(G_K, J[2]) \rightarrow \text{Br}(K)$ under the same assumption. Finally, we include a worked example demonstrating that we can improve the rank bound given by a 2-descent via computing the Cassels–Tate pairing.

Type
Research Article
Copyright
© The Author(s), 2024. Published by Cambridge University Press on behalf of Cambridge Philosophical Society

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