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.