English

Hyperelliptic curves over $\mathbb{F}_q$ and Gaussian hypergeometric series

Number Theory 2013-11-20 v1

Abstract

Let d2d\geq2 be an integer. Denote by EdE_d and EdE'_{d} the hyperelliptic curves over Fq\mathbb{F}_q given by Ed:y2=xd+ax+b   and   Ed:y2=xd+axd1+b,E_d: y^2=x^d+ax+b~~~ \text{and} ~~~E'_d: y^2=x^d+ax^{d-1}+b, respectively. We explicitly find the number of Fq\mathbb{F}_q-points on EdE_d and EdE'_d in terms of special values of dFd1{_{d}}F_{d-1} and d1Fd2{_{d-1}}F_{d-2} Gaussian hypergeometric series with characters of orders d1d-1, dd, 2(d1)2(d-1), 2d2d, and 2d(d1)2d(d-1) as parameters. This gives a solution to a problem posed by Ken Ono \cite[p. 204]{ono2} on special values of n+1Fn{_{n+1}}F_n Gaussian hypergeometric series for n>2n > 2. We also show that the results of Lennon \cite{lennon1} and the authors \cite{BK3} on trace of Frobenius of elliptic curves follow from the main results.

Keywords

Cite

@article{arxiv.1311.4695,
  title  = {Hyperelliptic curves over $\mathbb{F}_q$ and Gaussian hypergeometric series},
  author = {Rupam Barman and Gautam Kalita},
  journal= {arXiv preprint arXiv:1311.4695},
  year   = {2013}
}