Francesco Mazzocca

Maximal arcs in Desarguesian planes of odd order do not exist

Forq an odd prime power, and 1<n<q, the Desarguesian planePG(2,q) does not contain an(nq−q+n,n)-arc.

On the structure of 3-nets embedded in a projective plane

We investigate finite 3-nets embedded in a projective plane over a (finite or infinite) field of any characteristic p. Such an embedding is regular when each of the three classes of the 3-net comprises concurrent lines, and irregular otherwise. It is completely irregular when no class of the 3-net consists of concurrent lines. We are interested in embeddings of 3-nets which are irregular but the lines of one class are concurrent. For an irregular embedding of a 3-net of order n>=5 we prove that, if all lines from two classes are tangent to the same irreducible conic, then all lines from the third class are concurrent. We also prove the converse provided that the order n of the 3-net is smaller than p. In the complex plane, apart from a sporadic example of order n=5 due to Stipins [7], each known irregularly embedded 3-net has the property that all its lines are tangent to a plane cubic curve. Actually, the procedure of constructing irregular 3-nets with this property works over any field. In positive characteristic, we present some more examples for n>=5 and give a complete classification for n=4.

The Finite Field Kakeya Problem

A Besicovitch set in AG(n, q) is a set of points containing a line in every direction. The Kakeya problem is to determine the minimal size of such a set. We solve the Kakeya problem in the plane, and substantially improve the known bounds for n>4.

Nuclei of point sets of sizeq+1 contained in the union of two lines inPG(2,q)

AbstractWe give a complete classification for pairs (

Extensions of combinatorial geometries by the addition of a unique line

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Characterizations of Classical Algebraic Varieties in Some Papers of Giuseppe Tallini and Some Personal Memories of a Friend

(ℬ),ℬ) where

Blocking Sets in PG(r, qn)

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