1. New Steiner systems from old ones by paramodifications
- Author
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Mezőfi, Dávid and Nagy, Gábor P.
- Subjects
Mathematics - Combinatorics ,05B05, 51E05 - Abstract
Techniques of producing new combinatorial structures from old ones are commonly called trades. The switching principle applies for a broad class of designs: it is a local transformation that modifies two columns of the incidence matrix. In this paper, we present a construction, which is a generalization of the switching transform for the class of Steiner 2-designs. We call this construction paramodification of Steiner 2-designs, since it modifies the parallelism of a subsystem. We study in more detail the paramodifications of affine planes, Steiner triple systems, and abstract unitals. Computational results show that paramodification can construct many new unitals., Comment: Revised version based on remarks of anonymous referee
- Published
- 2020