On the Burness-Giudici Conjecture

Abstract

Let $G$ be a permutation group on a set $\Omega$. A subset of $\Omega$ is a base for $G$ if its pointwise stabilizer in $G$ is trivial. By $b(G)$ we denote the size of the smallest base of $G$. Every permutation group with $b(G)=2$ contains some regular suborbits. It is conjectured by Burness-Giudici in [4] that every primitive permutation group $G$ with $b(G)=2$ has the property that if $\alpha^g\not\in \Gamma$ then $\Gamma \cap \Gamma^g\neq \emptyset$, where $\Gamma$ is the union of all regular suborbits of $G$ relative to $\alpha$. An affirmative answer of the conjecture has been shown for many sporadic simple groups and some alternative groups in [4], but it is still open for simple groups of Lie-type. The first candidate of infinite family of simple groups of Lie-type we should work on might be $PSL(2,q)$, where $q\geq 5$. In this manuscript, we show the correctness of the conjecture for all the primitive groups with socle $PSL(2,q)$, see Theorem $1.3$.