Florian Reich

activity

20242026

collaborators

5 papers

math.CO2026

Menger's theorem for ends of digraphs

Florian Reich

Polat generalised Menger's theorem -- the maximum number of vertex-disjoint paths between two sets $A$ and $B$ equals the minimum size of an $A$ - $B$ separator -- to ends of undirec…

math.CO2025

Halin's grid theorem for digraphs

Florian Reich

Halin showed that every thick end of every graph contains an infinite grid. We extend Halin's theorem to digraphs. More precisely, we show that for every infinite family $\mathcal{…

math.CO2025

A star-comb lemma for infinite digraphs

Florian Reich

The star-comb lemma is a standard tool in infinite graph theory, which states that for every infinite set $U$ of vertices in a connected graph $G$ there exists either a subdivided…

math.CO2025

A star-comb lemma for finite digraphs

Florian Reich

It is well-known that for every set $U$ of vertices in a connected graph $G$ there is either a subdivided star in $G$ with a large number of leaves in $U$ , or a comb in $G$ with a…

math.CO2024

Generating strongly 2-connected digraphs

Meike Hatzel, Stephan Kreutzer, Evangelos Protopapas +3

We prove that there exist four operations such that given any two strongly $2$ -connected digraphs $H$ and $D$ where $H$ is a butterfly-minor of $D$ , there exists a sequence $D_0,\d…