Generalized GM-MDS: Polynomial Codes are Higher Order MDS

TL;DR

This paper extends the GM-MDS theorem to all polynomial codes and their duals, demonstrating that the generator matrices of these codes can attain all zero configurations, with implications for capacity-achieving list-decodable codes.

Contribution

It generalizes the GM-MDS theorem to polynomial and algebraic codes, including their duals, broadening the scope of MDS properties in coding theory.

Findings

GM-MDS applies to any polynomial code and its dual.

The theorem extends to algebraic codes on irreducible varieties.

Applications include constructing capacity-achieving list-decodable codes.

Abstract

The GM-MDS theorem, conjectured by Dau-Song-Dong-Yuen and proved by Lovett and Yildiz-Hassibi, shows that the generator matrices of Reed-Solomon codes can attain every possible configuration of zeros for an MDS code. The recently emerging theory of higher order MDS codes has connected the GM-MDS theorem to other important properties of Reed-Solomon codes, including showing that Reed-Solomon codes can achieve list decoding capacity, even over fields of size linear in the message length. A few works have extended the GM-MDS theorem to other families of codes, including Gabidulin and skew polynomial codes. In this paper, we generalize all these previous results by showing that the GM-MDS theorem applies to any polynomial code, i.e., a code where the columns of the generator matrix are obtained by evaluating linearly independent polynomials at different points. We also show that the GM-MDS theorem applies to dual codes of such polynomial codes, which is non-trivial since the dual of a polynomial code may not be a polynomial code. More generally, we show that GM-MDS theorem also holds for algebraic codes (and their duals) where columns of the generator matrix are chosen to be points on some irreducible variety which is not contained in a hyperplane through the origin. Our generalization has applications to constructing capacity-achieving list-decodable codes as shown in a follow-up work by Brakensiek-Dhar-Gopi-Zhang, where it is proved that randomly punctured algebraic-geometric (AG) codes achieve list-decoding capacity over constant-sized fields.