Glasnik Matematicki, Vol. 37, No.1 (2002), 1-12.

ON GROUPS E₂₅ · Z₄ AS AUTOMORPHISM GROUPS OF (100,45,20) SYMMETRIC DESIGNS

Vinko Buble, Anka Golemac and Tanja Vucicic

University of Split, Department of Mathematics, Teslina 12/III, 21000 Split, Croatia
e-mail: golemac@mapmf.pmfst.hr
e-mail: vucicic@mapmf.pmfst.hr

Abstract.   Nonabelian groups of order 100, that are extensions of the elementary abelian group E₂₅ by the group Z₄ are considered as possible automorphism groups of symmetric designs with parameters (100,45,20). By the action of these groups new (100,45,20) symmetric designs are constructed. Their full automorphism groups are given.

2000 Mathematics Subject Classification.   05B05.

Key words and phrases.   Symmetric designs, automorphism group, orbit structure, indexing.