Christian Reiher

activity

20242026

collaborators

11 papers

math.CO2026

Canonical Ramsey theorem for graphs with clean intersections

MatÃas AzÃ³car Carvajal, Ayush Basu, Christian Reiher +3

Extending earlier results of NeÅ¡etÅil and RÃ¶dl [Selective graphs and hypergraphs, Ann. Discrete Math. 3 (1978), 181--189], we show that for every ordered graph $F$ there exist a…

math.CO2026

Linearly distributive coherence in the absence of units

Max Demirdilek, Christian Reiher, Christoph Schweigert

Coherence in a monoidal category asserts that all morphisms built from structural isomorphisms with a fixed source and target coincide. These structural isomorphisms include, in pa…

math.CO2026

Large sum-free sets in finite vector spaces II

Christian Reiher, Sofia Zotova

Answering a question of Leo Versteegen, we prove that for $n \geq 3$ every sum-free set $A \subseteq F_{5}^{n}$ with $∣ A ∣ \geq 28 \cdot 5^{n - 3}$ is either contained in the union of t…

math.CO2026

The complete picture for clique factors in randomly perturbed graphs

Sylwia Antoniuk, Nina KamÄev, Christian Reiher +1

A randomly perturbed graph $G^{p} = G_{I^} \pm \cup G_{n, p}$ is obtained by taking a deterministic $n$ -vertex graph $G_{I^} \pm = (V, E)$ with minimum degree $I^´ (G) \geq I^\pm n$ and adding the edges o…

math.CO2025

Geometric constructions for Ramsey-TurÃ¡n theory

Hong Liu, Christian Reiher, Maryam Sharifzadeh +1

Combining two classical notions in extremal combinatorics, the study of Ramsey-TurÃ¡n theory seeks to determine, for integers $m \leq n$ and $p \leq q$ , the number $\mathsf{RT}_p(n,K…

math.CO2025

Unavoidable subgraphs in Ramsey graphs

Christian Reiher, VojtÄch RÃ¶dl, Mathias Schacht

We study subgraphs that appear in large Ramsey graphs for a given graph $F$ . The recent girth Ramsey theorem of the first two authors asserts that there are Ramsey graphs such that…