Séminaire Lotharingien de Combinatoire, B56f (2007), 31 pp.

Gregg Musiker

Combinatorial Aspects of Elliptic Curves

Abstract. Given an elliptic curve C, we study here Nk = #C(Fqk), the number of points of C over the finite field Fqk. This sequence of numbers, as k runs over positive integers, has numerous remarkable properties of a combinatorial flavor in addition to the usual number theoretical interpretations. In particular, we prove that Nk = -Wk(q,-N1), where Wk(q,t) is a (q,t)-analogue of the number of spanning trees of the wheel graph. Additionally we develop a determinantal formula for Nk, where the eigenvalues can be explicitly written in terms of q, N1, and roots of unity. We also discuss here a new sequence of bivariate polynomials related to the factorization of Nk, which we refer to as elliptic cyclotomic polynomials because of their various properties.

Received: October 27, 2006. Revised: June 22, 2007. Accepted: July 21, 2007.

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