Blocking sets of the classical unital

A non-classical unital of order four with many translations

We give a general construction for unitals of order q admitting an action of SU(2, q). The construction covers the classical hermitian unitals, Grüning’s unitals in Hall planes and at least one unital of order four where the translation centers fill precisely one block. For the latter unital, we determine the full group of automorphisms and show that there are no group-preserving embeddings int...

On the stability of small blocking sets

A stability theorem says that a nearly extremal object can be obtained from an extremal one by “small changes”. In this paper, we study the relation of sets having few 0-secants and blocking sets.

Sets of generators blocking all generators in finite classical polar spaces

We introduce generator blocking sets of finite classical polar spaces. These sets are a generalisation of maximal partial spreads. We prove a characterization of these minimal sets of the polar spaces Q(2n, q), Q(2n + 1, q) and H(2n, q), in terms of cones with vertex a subspace contained in the polar space and with base a generator blocking set in a polar space of rank 2. keywords: partial spre...

Blocking sets in handcuffed designs

In this paper we determine the spectrum of possible cardinalities of a blocking set in a H(v,3,A) and in a H(v,4,1). Moreover we construct, for each admissible ~9, a H(v,3,1) without blocking sets. Introduction A handcuffed design with parameters v, k, A, or for short an H(v,k,A), consists of a set of ordered k-subsets of a v-set, called handcuffed blocks. In a block (a., a z ' ... ,a!:) each e...

Blocking sets in chain geometries