Steiner t-Designs for Large t

One of the most central and long-standing open questions in combinatorial design theory concerns the existence of Steiner t -designs for large values of t . Although in his classical 1987 paper, L. Teirlinck has shown that non-trivial t -designs exist for all values of t , no non-trivial Steiner t -design with t > 5 has been constructed until now. Understandingly, the case t = 6 has received considerable attention. There has been recent progress concerning the existence of highly symmetric Steiner 6-designs: It is shown in [M. Huber, J. Algebr. Comb. 26 (2007), pp. 453---476] that no non-trivial flag-transitive Steiner 6-design can exist. In this paper, we announce that essentially also no block-transitive Steiner 6-design can exist.