Some rigid Steiner 5-designs



Hitherto, all known non-trivial Steiner systems S(5, k, v) have, as a group of automorphisms, either PSL(2, v−1) or PGL(2, (v−2)/2) × C2. In this article, systems S(5, 6, 72), S(5, 6, 84) and S(5, 6, 108) are constructed that have only the trivial automorphism group. © 2010 Wiley Periodicals, Inc. J Combin Designs 18:392–400, 2010