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Del Pezzo surfaces over finite fields and their Frobenius traces

Published online by Cambridge University Press:  10 April 2018

BARINDER BANWAIT
Affiliation:
CMR Surgical, Crome Lea Business Park, Madingley Road, Cambridge, CB23 7PH. e-mail: barinder.banwait@cmrsurgical.com
FRANCESC FITÉ
Affiliation:
Departament de Matemàtiques, Universitat Politècnica de Catalunya/BGSmath Edifici Omega, C/Jordi Girona 1–3, 08034 Barcelona, Catalonia. e-mail: francesc.fite@gmail.com
DANIEL LOUGHRAN
Affiliation:
School of Mathematics, University of Manchester, Oxford Road, Manchester, M13 9PL. e-mail: daniel.loughran@manchester.ac.uk

Abstract

Let S be a smooth cubic surface over a finite field $\mathbb{F}$q. It is known that #S($\mathbb{F}$q) = 1 + aq + q2 for some a ∈ {−2, −1, 0, 1, 2, 3, 4, 5, 7}. Serre has asked which values of a can arise for a given q. Building on special cases treated by Swinnerton–Dyer, we give a complete answer to this question. We also answer the analogous question for other del Pezzo surfaces, and consider the inverse Galois problem for del Pezzo surfaces over finite fields. Finally we give a corrected version of Manin's and Swinnerton–Dyer's tables on cubic surfaces over finite fields.

Type
Research Article
Copyright
Copyright © Cambridge Philosophical Society 2018 

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