Sophie Spirkl

collaborators

3 papers

math.CO2025

The structure of $Δ (1, 2, 2)$ -free tournaments

Seokbeom Kim, Taite LaGrange, Mathieu Rundström +2

We extend the list of tournaments $S$ for which the complete structural description for tournaments excluding $S$ as a subtournament is known. Specifically, let $Δ (1, 2, 2)$ be a t…

math.CO2025

Intersections of graphs and $χ$ -boundedness

Aristotelis Chaniotis, Hidde Koerts, Sophie Spirkl

Given $k$ graphs $G_{1}, \dots, G_{k}$ , their intersection is the graph $(\cap_{i \in [k]} V (G_{i}), \cap_{i \in [k]} E (G_{i}))$ . Given $k$ graph classes $\mathcal{G}_{1}, \ldots , \m…

math.CO2025

Orientations of cycles in digraphs of high chromatic number and high minimum out-degree

Hidde Koerts, Benjamin Moore, Sophie Spirkl

We characterize all orientations of cycles $C$ for which for every fixed $ε > 0$ there exists a constant $c \geq 1$ such that every digraph $D$ without loops or parallel…

The structure of Δ(1,2,2)-free tournaments

Intersections of graphs and χ-boundedness

Orientations of cycles in digraphs of high chromatic number and high minimum out-degree

The structure of $Δ (1, 2, 2)$ -free tournaments

Intersections of graphs and $χ$ -boundedness