Flag-transitive $4$-designs and $PSL(2,q)$ groups

Huili Dong

This paper considers flag-transitive $4$-$(q+1,k,\lambda )$ designs with $\lambda \ge 5$ and $q+1>k>4$. Let the automorphism group of a design $\mathcal{D}$ be a simple group $G=PSL(2,q)$. Depend on…