On designs constructed by group actions

M. R. Darafsheh1, A. R. Ashrafi2, M. Khademi3
1School of Mathematics, Statistics and Computer Science, College of Science, University of Tehran, Tehran, Iran.
2Department of Mathematics, Faculty of Science, University of Kashan, Kashan, Iran.
3Islamic Azad University, South Tehran Branch, Tehran, Iran.

Abstract

Using the action of the linear fractional groups \( L_2(q) \), where \( q = 8, 25, 27, 29, 31 \) and \( 32 \), some \( 1 \)-designs are constructed. It is shown that subgroups of the automorphism group of \( L_2(q) \) appear as the full automorphism group of the constructed designs. In the cases \( q = 8 \) and \( 32 \), it is shown that the symmetric groups \( \mathbb{S}_9 \) and \( \mathbb{S}_{33} \), respectively, appear as the automorphism group of one of the constructed designs.