Multivariate Goppa codes
Hiram H. López, Gretchen L. Matthews
TL;DR
This work generalizes classical Goppa codes to a multivariate setting by defining $\Gamma(\mathcal{S},g)$ over a Cartesian product $\mathcal{S}$ and a factorable polynomial $g=g_1\cdots g_m$. It provides a parity-check description of the codes using a tensor product of generalized Reed-Solomon codes via $\mathrm{T}(\mathcal{S},\mathbf{k},g)$ and shows $\Gamma(\mathcal{S},g)$ is the $\mathbb{F}_q$-subfield subcode of the dual of $\mathrm{T}(\mathcal{S},g)$, and also that $\Gamma(\mathcal{S},g)$ is a subfield subcode of the augmented Cartesian code $\mathrm{ACar}(\mathcal{S},g)$. By relating these three families, the paper derives parameter bounds, characterizes hulls and subcodes, and constructs entanglement-assisted quantum error-correcting codes and LCD/self-orthogonal/self-dual codes, including long-length families not bounded by the field size. The results unify and extend prior work on Goppa codes, GRS tensors, and augmented codes, with practical implications for quantum coding and code design.
Abstract
In this paper, we introduce multivariate Goppa codes, which contain as a special case the well-known, classical Goppa codes. We provide a parity check matrix for a multivariate Goppa code in terms of a tensor product of generalized Reed-Solomon codes. We prove that multivariate Goppa codes are subfield subcodes of augmented Cartesian codes. By showing how this new family of codes relates to tensor products of generalized Reed-Solomon codes and augmented codes, we obtain information about the parameters, subcodes, duals, and hulls of multivariate Goppa codes. We see that in certain cases, the hulls of multivariate Goppa codes (resp., tensor product of generalized Reed-Solomon codes), are also multivariate Goppa codes (resp. tensor product of generalized Reed-Solomon codes). We utilize the multivariate Goppa codes to obtain entanglement-assisted quantum error-correcting codes and to build families of long LCD, self-dual, or self-orthogonal codes.
