Flynn, E. V. (2009) *Homogeneous Spaces and Degree 4 del Pezzo Surfaces.* Manuscripta Mathematica, 129 . pp. 369-380. ISSN 0025-2611

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## Abstract

It is known that, given a genus 2 curve C : y^2 = f(x), where f(x) is quintic and defined over a field K, of characteristic different from 2, and given a homogeneous space H_delta for complete 2-descent on the Jacobian of C, there is a V_delta (which we shall describe), which is a degree 4 del Pezzo surface defined over K, such that H_delta(K) nonempty implies V_delta(K) nonempty. We shall prove that every degree 4 del Pezzo surface V, defined over K, arises in this way; furthermore, we shall show explicitly how, given V, to find C and delta such that V = V_delta, up to a linear change in variable defined over K. We shall also apply this relationship to Hurlimann's example of a degree 4 del Pezzo surface violating the Hasse principle, and derive an explicit parametrised infinite family of genus 2 curves, defined over Q, whose Jacobians have nontrivial members of the Shafarevich-Tate group. This example will differ from previous examples in the literature by having only two Q-rational Weierstrass points.

Item Type: | Article |
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Subjects: | H - N > Number theory |

Research Groups: | Number Theory Group |

ID Code: | 803 |

Deposited By: | E. Victor Flynn |

Deposited On: | 01 Sep 2009 08:34 |

Last Modified: | 01 Sep 2009 08:34 |

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