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Abstract

One-point codes are those algebraic-geometry codes for which the associated divisor is a non-negative multiple of a single point. Evaluation codes were defined in order to give an algebraic generalization of both one-point algebraic-geometry codes and Reed–Muller codes. Given an \mathbbFq{\mathbb{F}}_q-algebra A, an order function r\rho on A and given a surjective \mathbbFq{\mathbb{F}}_q-morphism of algebras j: A® \mathbbFqn\varphi: A\rightarrow {\mathbb{F}}_q^{n}, the ith evaluation code with respect to A,r,jA,\rho,\varphi is defined as the code Ci=j({f Î A: r(f) £ i})C_i=\varphi(\{f\in A: \rho(f)\leq i\}) . In this work it is shown that under a certain hypothesis on the \mathbbFq\mathbb{F}_q-algebra A, not only any evaluation code is a one-point code, but any sequence of evaluation codes is a sequence of one-point codes. This hypothesis on A is that its field of fractions is a function field over \mathbbFq\mathbb{F}_q and that A is integrally closed. Moreover, we see that a sequence of algebraic-geometry codes G i with associated divisors Gi\Gamma_i is the sequence of evaluation codes associated to some \mathbbFq{\mathbb{F}}_q-algebra A, some order function r\rho and some surjective morphism j\varphi with {f Î A: r(f) £ i}=L(Gi)\{f\in A: \rho(f)\leq i\}={\mathcal{L}}(\Gamma_i) if and only if it is a sequence of one-point codes.

Keywords  Algebraic-geometry code - One-point code - Evaluation code

AMS Classifications  94B27 - 11T71 - 14G50


Communicated by D. Jungnickel.

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