Computing zeta functions of Artin-Schreier curves over finite fields II

  • Authors:
  • Alan G. B. Lauder;Daqing Wan

  • Affiliations:
  • Mathematical Institute, Oxford University, 24-29 St. Giles, Oxford OX1 3LB, UK;Department of Mathematics, University of California, Irvine, CA and Institute of Mathematics, Chinese Academy of Sciences, Beijing, People's Republic of China

  • Venue:
  • Journal of Complexity - Special issue on coding and cryptography
  • Year:
  • 2004

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Abstract

We describe a method which may be used to compute the zeta function of an arbitrary Artin-Schreier cover of the projective line over a finite field. Specifically, for covers defined by equations of the form Zp -Z =f(X) we present, and give the complexity analysis of, an algorithm for the case in which f(X) is a rational function whose poles all have order 1. However, we only prove the correctness of this algorithm when the field characteristic is at least 5. The algorithm is based upon a cohomological formula for the L-function of an additive character sum. One consequence is a practical method of finding the order of the group of rational points on the Jacobian of a hyperelliptic curve in characteristic 2.