More on matrix semigroup homomorphisms
The author studies non-degenerate irreducible homomorphisms from the multiplicative semigroup of all \(2\times 2\)-complex matrices to the semigroup of \(n\times n\)-complex matrices. If such a homomorphism maps a cyclic unipotent to a cyclic unipotent, it is the composition of a symmetric power, a field homomorphism used entrywise, and a matrix conjugation. In the case \(n=4\) all non-degenerate irreducible homomorphisms are characterized.
scientific article; zbMATH DE number 1758609