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1 vote
1 answer
333 views

Szemerédi–Trotter type theorem in finite field

This question is about the content of this paper by J. Bourgain, N. Katz, T. Tao. In the final step (page 18) of the proof of Szemerédi-Trotter type theorem, we have already known $$|A''+A''|\lesssim ...
4 votes
1 answer
561 views

Why should it be hard to generalize Dvir's proof of the finite field Kakeya conjecture to the Euclidean case?

Let $q$ be prime and let $q\delta \sim 1.$ Let $K$ be any set of $C_n\delta$-separated tubes in $B(0,2)$, where $C_n$ is some constant depending on $n$. Let us consider a grid of $q^n$ points scaled ...
6 votes
1 answer
458 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 $q(q+1)/2 + (q-1)/2$ ...
11 votes
2 answers
788 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,...
4 votes
1 answer
463 views

Covering all, but $k$ points with affine subspaces

For non-negative integer $d\le n$ and $k\le 2^n$, how many affine subspaces of co-dimension $d$ are needed to cover all, but exactly $k$ elements of the vector space ${\mathbb F}_2^n$, and what are ...