English

The partition of $PG(2,q^3)$ arising from an order 3 planar collineation

Combinatorics 2025-03-25 v1

Abstract

Let ϕ\phi be a collineation of order 3 acting on PG(2,q3)PG(2,q^3) whose fixed points are exactly an Fq\mathbb F_q-plane πq\pi_q. Let TT be a point whose orbit under ϕ\phi is a triangle and let SGS_G be the subgroup of PGL(3,q3)PGL(3,q^3) that fixes setwise the Fq\mathbb F_q-plane πq\pi_q and fixes setwise the line TϕTϕ2T^\phi T^{\phi^2}. The point orbits of SGS_G form a partition of the points of PG(2,q3)PG(2,q^3) and consist of: the singletons T,Tϕ,Tϕ2T,T^\phi, T^{\phi^2}; scattered linear sets on the sides of the triangle TTϕTϕ2T T^\phi T^{\phi^2}; and Fq\mathbb F_q-planes. This article studies the structure of this partition, looking at maps that permute elements of the partition. The motivation in studying this partition lies in its application to the construction of the Figueroa projective plane, and the article concludes with a characterisation in this setting.

Keywords

Cite

@article{arxiv.2503.18262,
  title  = {The partition of $PG(2,q^3)$ arising from an order 3 planar collineation},
  author = {S. G. Barwick and Alice M. W. Hui and Wen-Ai Jackson},
  journal= {arXiv preprint arXiv:2503.18262},
  year   = {2025}
}