On $p$-schemes of order $p^3$

Abstract

Let $(X,S)$ be a $p$-scheme of order $p^3$ and $T$ the thin residue of $S$. Now we assume that $T$ has valency $p^2$. It is easy to see that one of the following holds: (i) $|T|=p^2$ and $T\simeq C_{p^2}$; (ii) $|T|=p^2$ and $T\simeq C_p\times C_p$; (iii) $|T|<p^2$. It is known that $(X,S)$ is Schurian if (i) holds. If (ii) holds, we will show that $(X,S)$ induces a partial linear space on $X/T$. Moreover, the character degrees of $(X,S)$ coincide with the sizes of the lines of the partial linear space. Under the assumption (iii) we will show a construction of non-Schurian $p$-schemes which are algebraically isomorphic to a Schurian $p$-scheme of order $p^3$.