$(d,\textbf{\sigma})$-Veronese variety and some applications

Abstract

Let $\mathbb{K}$ be the Galois field $\mathbb{F}_{q^t}$ of order $q^t, q=p^e, p$ a prime, $A=\mathrm{Aut}(\mathbb{K})$ be the automorphism group of $\mathbb{K}$ and $\boldsymbol{\sigma}=(\sigma_0,\ldots, \sigma_{d-1}) \in A^d$, $d \geq 1$. In this paper the following generalization of the Veronese map is studied: $$ \nu_{d,\boldsymbol{\sigma}} : \langle v\rangle \in \mathrm{PG}(n-1,\mathbb{K}) \longrightarrow \langle v^{\sigma_0} \otimes v^{\sigma_1} \otimes \cdots \otimes v^{\sigma_{d-1}}\rangle \in \mathrm{PG} (n^d-1,\mathbb{K} ). $$ Its image will be called the $(d,\boldsymbol{\sigma})$-$Veronese$ $variety$ $\mathcal{V}_{d,\boldsymbol{\sigma}}$. Here, we will show that $\mathcal{V}_{d,\boldsymbol{\sigma}}$ is the Grassmann embedding of a normal rational scroll and any $d+1$ points of it are linearly independent. We give a characterization of $d+2$ linearly dependent points of $\mathcal{V}_{d,\boldsymbol{\sigma}}$ and for some choices of parameters, $\mathcal{V}_{p,\boldsymbol{\sigma}}$ is the normal rational curve; for $p=2$, it can be the Segre's arc of $\mathrm{PG}(3,q^t)$; for $p=3$ $\mathcal{V}_{p,\boldsymbol{\sigma}}$ can be also a $|\mathcal{V}_{p,\boldsymbol{\sigma}}|$-track of $\mathrm{PG}(5,q^t)$. Finally, investigate the link between such points sets and a linear code $\mathcal{C}_{d,\boldsymbol{\sigma}}$ that can be associated to the variety, obtaining examples of MDS and almost MDS codes.