Weierstrass Pairs and Minimum Distance of Goppa Codes.
Gretchen L. Matthews · 1999
We prove that elements of the Weierstrass gap set of a pair of points may be used to define a geometric Goppa code that has minimum distance greater than the usual lower bound. We determine the Weierstrass gap set of a pair of any two Weierstrass points on a Hermitian curve and use this to increase the lower bound on the minimum distance of certain codes defined using a linear combination of the two points. In particular, we obtain some two-point codes on a Hermitian curve that have better parameters than the one-point code on this curve with the same dimension. These results generalize to certain codes defined using an m-tuple of points on a smooth projective absolutely irreducible curve.