Arcs and Ovals in the Hermitian and Ree Unitals

The hermitian unitals U(q) and the Ree unitals RU(q) are examined for the existence of ovals and arcs. It is shown that U(q) does not have ovals for q > 2 and that RU(q), like U(q), is embedded in a much larger design with block intersections of cardinality ⩽ 2. Arcs of size 3q + 1 are constructed for the Ree unitals RU(q); they are ovals only in the case q = 3. In this case, U(3) and RU(3) are embedded in the same design and its automorphism group, the symplectic group Sp(6, 2), contains the automorphism groups of both the unitals; the coding-theoretic aspects are elucidated