Core Concepts
A new class of non-linear maximum rank distance (MRD) codes is constructed using a geometric approach involving cones over exterior sets in finite projective spaces.
Abstract
The article presents a geometric construction of a new family of non-linear MRD codes. The key insights are:
The codes are obtained from a cone in the finite projective space PG(n-1, q^n), where the vertex of the cone is a proper subspace and the base is a special point set that is skew with the vertex.
The base of the cone is linked to non-linear MRD codes constructed in prior work, which can be obtained by puncturing the codes in the new family.
It is shown that this new class of codes is not equivalent to the non-linear MRD codes constructed by Otal and Özbudak.
The construction involves the following steps:
Defining an (n-k+1)-embedding Γ of the canonical subgeometry Σ in PG(n-1, q^n).
Identifying a maximum exterior set E with respect to Ω_n-k-1(Γ).
Constructing the cone K(Λ^, E), where Λ^ is a (k-2)-dimensional subspace disjoint from Σ.
Proving that K(Λ^*, E) is a maximum exterior set with respect to Ω_n-k-1(Σ).
Showing that the resulting non-linear MRD code Cσ,T, where T is a subset of F_q^*, contains the codes constructed in prior work as punctured versions.
Stats
The size of the exterior set E is given as:
|E| ≤ (q^(n-h-1) - 1) / (q - 1), where 0 ≤ h ≤ n-1.
The size of the cone K(Λ^, E) is given as:
|K(Λ^, E)| = (q^nk - 1) / (q - 1).
Quotes
"The set X is the Cσ_F-set with vertices A and B generated by a σ-collineation Φ between the star of lines through A and B contained in Λ."
"The punctured code C^[k-2]_σ,T ⊂ F^((n-k+2)×n)_q obtained from Cσ,T by deleting the last (k-2) rows is exactly the code constructed in [8, Theorem 5.1], while for k = 2 the code appeared in [9] and for n = 3, k = 2 in [2]."