The automorphism group of NU(3,q2).

Let H (n , q 2) be a non-degenerate Hermitian variety of P G (n , q 2) , n ≥ 2 . Let N U (n + 1 , q 2) be the graph whose vertices are the points of P G (n , q 2) \ H (n , q 2) and two vertices u, v are adjacent if the line joining u and v is tangent to H (n , q 2) . Then N U (n + 1 , q 2) is a strongly regular graph. In this paper we show that the automorphism group of the graph N U (3 , q 2) is isomorphic either to P Γ U (3 , q) , the automorphism group of the projective unitary group PGU(3, q), or to S 3 ≀ S 4 , according as q ≠ 2 , or q = 2 . [ABSTRACT FROM AUTHOR]