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Abstract incidence geometries like projective spaces, polar spaces, generalized polygons, as well as incidence problems in the real or complex Euclidean spaces (eg. Szemerédi–Trotter theorem).

2 votes

Reference on the Veblen-Young characterization of projective spaces

Here are some modern treatments: Projective Geometries: From Foundations to Applications, Albrecht Beutelspacher (1998) - see chapter 3 for the Veblen-Young characterisation. Points and Lines, Erne …
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2 votes

Covering all, but $k$ points with affine subspaces

Here are some partial answers to your question. Let $A = A_1 \times \dots \times A_n \subseteq F^n$ be a finite grid. Alon and Furedi proved that you need at least $\sum (\# A - 1)$ hyperplanes to …
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3 votes

Blocking sets in three dimensional finite affine spaces

Here is an improvement of the upper bound which I found in ``The polynomial method in Galois geometries'' by Simeon Ball. See page number 4. The known constructions are somewhat crude. For exampl …
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6 votes
1 answer
454 views

Applications of small Kakeya sets over finite fields

It was proved by Dvir that a Kakeya set in $\mathbb{F}_q^n$ has size at least $q^n/n!$, a bound which was later improved to $q^n/2^n$. For $n = 2$ and $q$ odd the exact bound is $q(q+1)/2 + (q-1)/2$ …
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11 votes
2 answers
781 views

Blocking sets in three dimensional finite affine spaces

What is the smallest possible size of a set of points in $\mathbb{F}_q^3$ which intersects (blocks) every line? Clearly the union of three affine hyperplanes that intersect in a singleton, say $x = 0 …
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