Twisted group codes of dimension 2 and 3
Abstract
It is known that all group codes of dimension at most $3$ are permutation equivalent to abelian group codes. We prove that twisted group codes of dimension at most $3$ are monomially equivalent either to an abelian group code or to an irreducible constacyclic code, and in the second case we describe the code explicitly by means of a trace map. Monomial equivalence cannot be replaced by permutation equivalence, and the second case cannot be avoided: the ternary tetracode is an ideal of π½3[x]/(x4+1) but it is not monomially equivalent to any group code. More generally, we give two infinite families, in dimensions $2$ and $3$, of irreducible constacyclic codes which attain the Griesmer bound, whereas every group code with the same length and dimension has smaller minimum distance.
Related
BibTeX
@misc{sanchez2026twisted,
title = {{Twisted group codes of dimension 2 and 3}},
author = {Alvaro Otero Sanchez},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.28297},
eprint = {2610.28297},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.28297},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Twisted group codes of dimension 2 and 3
AU - Alvaro Otero Sanchez
PY - 2026
DA - 2026/10/27
PB - arXiv
DO - 10.48550/arxiv.2610.28297
UR - https://arxiv.org/abs/2610.28297
AB - It is known that all group codes of dimension at most $3$ are permutation equivalent to abelian group codes. We prove that twisted group codes of dimension at most $3$ are monomially equivalent either to an abelian group code or to an irreducible constacyclic code, and in the second case we describe the code explicitly by means of a trace map. Monomial equivalence cannot be replaced by permutation equivalence, and the second case cannot be avoided: the ternary tetracode is an ideal of π½_3[x]/(x^4+1) but it is not monomially equivalent to any group code. More generally, we give two infinite families, in dimensions $2$ and $3$, of irreducible constacyclic codes which attain the Griesmer bound, whereas every group code with the same length and dimension has smaller minimum distance.
ER -