English

On $\alpha$-points of $q$-analogs of the Fano plane

Combinatorics 2025-10-02 v1

Abstract

Arguably, the most important open problem in the theory of qq-analogs of designs is the question for the existence of a qq-analog DD of the Fano plane. It is undecided for every single prime power value q2q \geq 2. A point PP is called an α\alpha-point of DD if the derived design of DD in PP is a geometric spread. In 1996, Simon Thomas has shown that there must always exist at least one non-α\alpha-point. For the binary case q=2q = 2, Olof Heden and Papa Sissokho have improved this result in 2016 by showing that the non-α\alpha-points must form a blocking set with respect to the hyperplanes. In this article, we show that a hyperplane consisting only of α\alpha-points implies the existence of a partiton of the symplectic generalized quadrangle W(q)W(q) into spreads. As a consequence, the statement of Heden and Sissokho is generalized to all primes qq and all even values of qq.

Keywords

Cite

@article{arxiv.2105.00365,
  title  = {On $\alpha$-points of $q$-analogs of the Fano plane},
  author = {Michael Kiermaier},
  journal= {arXiv preprint arXiv:2105.00365},
  year   = {2025}
}