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A large driver of the complexity of graph learning is the interplay between structure and features. When analyzing the expressivity of graph neural networks, however, existing approaches ignore features in favor of structure, making it…

Machine Learning · Computer Science 2026-03-04 Martin Carrasco , Olga Zaghen , Kavir Sumaraj , Erik Bekkers , Bastian Rieck

The neighborhood complex of a graph was introduced by Lov\'asz to provide topological lower bounds on chromatic number. More general homomorphism complexes of graphs were further studied by Babson and Kozlov. Such `Hom complexes' are also…

Combinatorics · Mathematics 2023-08-16 Anton Dochtermann , Anurag Singh

Let $A(G)$ and $B(H)$ be the Fourier and Fourier-Stieltjes algebras of locally compact groups $G$ and $H$, respectively. Ilie and Spronk have shown that continuous piecewise affine maps $\alpha: Y \subseteq H\rightarrow G$ induce completely…

Functional Analysis · Mathematics 2022-06-01 Matthew Daws

We introduce a metric homotopy theory, which we call Moderately Discontinuous Homotopy, designed to capture Lipschitz properties of metric singular subanalytic germs. It matches with the Moderately Discontinuous Homology theory receantly…

Algebraic Geometry · Mathematics 2020-07-06 J. Fernandez de Bobadilla , S. Heinze , M. Pe Pereira

A structure is called homogeneous if every isomorphism between finitely induced substructures of the structure extends to an automorphism of the structure. Recently, P. J. Cameron and J. Ne\v{s}et\v{r}il introduced a relaxed version of…

Combinatorics · Mathematics 2009-12-31 Dragan Mašulović , Rajko Nenadov , Nemanja Škorić

The well-known Erd\H{o}s-Hajnal conjecture states that for any graph $F$, there exists $\epsilon>0$ such that every $n$-vertex graph $G$ that contains no induced copy of $F$ has a homogeneous set of size at least $n^{\epsilon}$. We consider…

Combinatorics · Mathematics 2023-03-20 Maria Axenovich , Dhruv Mubayi , Lea Weber

Recent results show that the structural similarity of graphs can be characterized by counting homomorphisms to them: the Tree Theorem states that the well-known color-refinement algorithm does not distinguish two graphs G and H if and only…

Discrete Mathematics · Computer Science 2019-04-01 Jan Böker

For any countably infinite graph $G$, Ramsey's theorem guarantees an infinite monochromatic copy of $G$ in any $r$-coloring of the edges of the countably infinite complete graph $K_\mathbb{N}$. Taking this a step further, it is natural to…

Combinatorics · Mathematics 2018-08-16 Louis DeBiasio , Paul McKenney

The distinguishing number of a graph $G$ is the smallest positive integer $r$ such that $G$ has a labeling of its vertices with $r$ labels for which there is no non-trivial automorphism of $G$ preserving these labels. Albertson and Collins…

Logic · Mathematics 2008-04-28 C. Laflamme , L. Nguyen Van Thé , N. W. Sauer

I prove that the Borel directed graphs whose vertex set admits a partition into two Borel acyclic sets form a $\mathbf\Sigma^1_2$-complete set; equivalently, that deciding whether a Borel directed graph has Borel dichromatic number at…

Logic · Mathematics 2026-04-08 Tonatiuh Matos-Wiederhold

We consider the problem of finding a homomorphism from an input digraph $G$ to a fixed digraph $H$. We show that if $H$ admits a weak near unanimity polymorphism $\phi$ then deciding whether $G$ admits a homomorphism to $H$ (HOM($H$)) is…

Computational Complexity · Computer Science 2020-11-24 Tomas Feder , Jeff Kinne , Ashwin Murali , Arash Rafiey

The celebrated Erd\H{o}s-Hajnal conjecture says that any graph without a fixed induced subgraph $H$ contains a very large homogeneous set. A direct analog of this conjecture is not true for hypergraphs. In this paper we present two natural…

Combinatorics · Mathematics 2024-12-02 Fabian Arnold , Lior Gishboliner , Benny Sudakov

The study of graph discrepancy problems, initiated by Erd\H{o}s in the 1960s, has received renewed attention in recent years. In general, given a $2$-edge-coloured graph $G$, one is interested in embedding a copy of a graph $H$ in $G$ with…

Combinatorics · Mathematics 2024-06-28 Andrea Freschi , Allan Lo

This is the third of a series of four papers in which we prove the following relaxation of the Loebl-Komlos-Sos Conjecture: For every $\alpha>0$ there exists a number $k_0$ such that for every $k>k_0$ every $n$-vertex graph $G$ with at…

Combinatorics · Mathematics 2017-07-31 Jan Hladký , János Komlós , Diana Piguet , Miklós Simonovits , Maya J. Stein , Endre Szemerédi

We introduce a new type of examples of bounded degree acyclic Borel graphs and study their combinatorial properties in the context of descriptive combinatorics, using a generalization of the determinacy method of Marks. The motivation for…

We show that for every ordinal $\alpha \in [1, \omega_1)$ there is a closed set $F \subset 2^\omega \times \omega^\omega$ such that for every $x \in 2^\omega$ the section $\{y\in \omega^\omega; (x,y) \in F\}$ is a two-point set and $F$…

Logic · Mathematics 2020-10-07 P. Holicky , M. Zeleny

In this paper we resolve the complexity of the isomorphism problem on all but finitely many of the graph classes characterized by two forbidden induced subgraphs. To this end we develop new techniques applicable for the structural and…

Discrete Mathematics · Computer Science 2014-11-10 Pascal Schweitzer

Confirming a conjecture of Erd\H{o}s on the chromatic number of Kneser hypergraphs, Alon, Frankl and Lov\'asz proved that in any $q$-colouring of the edges of the complete $r$-uniform hypergraph, there exists a monochromatic matching of…

Combinatorics · Mathematics 2026-02-23 Lior Gishboliner , Stefan Glock , Peleg Michaeli , Amedeo Sgueglia

Two major milestones on the road to the full complexity dichotomy for finite-domain constraint satisfaction problems were Bulatov's proof of the dichotomy for conservative templates, and the structural dichotomy for smooth digraphs of…

Logic in Computer Science · Computer Science 2026-04-07 Johanna Brunar , Marcin Kozik , Tomáš Nagy , Michael Pinsker

Conlon, Gowers, Samotij, and Schacht showed that for a given graph $H$ and a constant $\gamma > 0$, there exists $C > 0$ such that if $p \ge Cn^{-1/m_2(H)}$ then asymptotically almost surely every spanning subgraph $G$ of the random graph…

Combinatorics · Mathematics 2016-11-30 Rajko Nenadov , Nemanja Škorić
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