A strengthening of Halin's grid theorem

Abstract

We show that for every infinite collection $\mathcal{R}$ of disjoint equivalent rays in a graph $G$ there is a subdivision of the hexagonal half-grid in $G$ such that all its vertical rays belong to $\mathcal{R}$. This result strengthens Halin's grid theorem by giving control over which specific set of rays is used, while its proof is significantly shorter.

4 pages, 2 figures