A characterisation of classical unitals.
A unital in a Desarguesian projective plane \(PG(2,q)\), \(q\) square, is a point set consisting of \(q \sqrt{q} +1\) points such that any line of \(PG(2,q)\) meets it in either \(1\) point or \(\sqrt{q} +1\) points. The paper under review presents a different and shorter proof of a result due to \textit{A. Cossidente, G. L. Ebert} and \textit{G. Korchmaros} [Arch. Math. 74, 1--5 (2000; Zbl 0961.51006)] characterising classical unitals, i.e. unitals consisting of the absolute points and non-absolute lines with respect to a unitary polarity of \(PG(2,q)\).
scientific article; zbMATH DE number 1890533