An automorphism of the symplectic group Sp4(2n)

Abstract

In his discussion (3) of automorphisms of finite simple linear groups, Steinberg shows that the group denoted by B2(K) admits graph automorphisms when K is a perfect field of characteristic 2. The group B2(K) is identified in (2) as the symplectic group Sp4(K) when K is finite and of characteristic 2, and it is the object of this note to give, by means of this identification, an explicit description of the graph automorphisms of B2(2n).