A note on short minimal codes from subgeometries
Sam Adriaensen, Peter Sziklai, Zsuzsa Weiner
TL;DR
The paper addresses the existence of three $\mathbb{F}_q$-subgeometries in $\mathrm{PG}(3,q^3)$ whose union forms a strong blocking set, which yields linear minimal codes with parameters $[3(q^2+1)(q+1),4]_{q^3}$ for all prime powers $q$. It provides a short, geometrically flavored proof for odd $q>9$ by leveraging the theory of small blocking sets in projective planes and a construction based on disjoint subgeometries of subspaces. The key contribution is showing, via $\mathbb{F}_q$-subgeometries arranged through $R$-independence, that such unions yield strong blocking sets of the desired size, and applying this to reproduce the BCMP result with a streamlined argument. This work clarifies the connection between small blocking sets in $\mathrm{PG}(2,q)$ and minimal codes, offering a more accessible route to the known $[3(q^2+1)(q+1),4]_{q^3}$ codes and suggesting avenues for extensions to higher values of $k$.
Abstract
In a 2022, Bartoli, Cossidente, Marino, and Pavese proved that in the projective space ${\rm PG}(3,q^3)$, one can find three $\mathbb F_q$-subgeometries such that the union of their point sets is a strong blocking set. This proves the existence of linear minimal codes with parameters $[3(q^2+1)(q+1),4]_{q^3}$ for every prime power $q$. We give a short proof of this result for odd values of $q > 9$, using the theory of small blocking sets in projective planes.
