Equivalence and automorphism groups of two families of maximum scattered linear sets

Linear set in projective spaces over finite fields plays central roles in the study of blocking sets, semifields, rank-metric codes and etc. A linear set with the largest possible cardinality and the maximum rank is called maximum scattered. Despite two decades of study, there are only a few number of known maximum scattered linear sets in projective lines, including the family constructed by Csajb\'ok, Marino, Polverino and Zanella 2018, and the family constructed by Csajb\'ok, Marino, Zullo 2018 (also Marino, Montanucci, and Zullo 2020). This paper aims to solve the equivalence problem of the linear sets in each of these families and to determine their automorphism groups.Comment: This is an English translation of the original Chinese version published in Scientia Sinica Mathematic

A new family of MRD-codes

We introduce a family of linear sets of PG(1,q^2n) arising from maximum scattered linear sets of pseudoregulus type of PG(3,q^n). For n=3,4 and for certain values of the parameters we show that these linear sets of PG(1,q^2n) are maximum scattered and they yield new MRD-codes with parameters (6,6,q;5) for q>2 and with parameters (8,8,q;7) for q odd

Field reduction and linear sets in finite geometry

Based on the simple and well understood concept of subfields in a finite field, the technique called `field reduction' has proved to be a very useful and powerful tool in finite geometry. In this paper we elaborate on this technique. Field reduction for projective and polar spaces is formalized and the links with Desarguesian spreads and linear sets are explained in detail. Recent results and some fundamental ques- tions about linear sets and scattered spaces are studied. The relevance of field reduction is illustrated by discussing applications to blocking sets and semifields