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A graph on $n$ vertices is said to be \emph{$C$-Ramsey} if every clique or independent set of the graph has size at most $C \log n$. The only known constructions of Ramsey graphs are probabilistic in nature, and it is generally believed…

Combinatorics · Mathematics 2017-09-08 Bhargav Narayanan , Julian Sahasrabudhe , István Tomon

The notions of bounded expansion and nowhere denseness not only offer robust and general definitions of uniform sparseness of graphs, they also describe the tractability boundary for several important algorithmic questions. In this paper we…

Discrete Mathematics · Computer Science 2019-09-25 Wojciech Nadara , Marcin Pilipczuk , Roman Rabinovich , Felix Reidl , Sebastian Siebertz

In this work, we consider an extension of graphical models to random graphs, trees, and other objects. To do this, many fundamental concepts for multivariate random variables (e.g., marginal variables, Gibbs distribution, Markov properties)…

Machine Learning · Statistics 2017-05-08 Neil Hallonquist

We establish the conditions under which several algorithmically exploitable structural features hold for random intersection graphs, a natural model for many real-world networks where edges correspond to shared attributes. Specifically, we…

Social and Information Networks · Computer Science 2017-02-10 Matthew Farrell , Timothy Goodrich , Nathan Lemons , Felix Reidl , Fernando Sánchez Villaamil , Blair D. Sullivan

In this paper we introduce a new topological Ramsey space whose elements are infinite ordered polyhedra. Then, we show as an application that the set of finite polyhedra satisfies two types of Ramsey property: one, when viewed as a category…

Combinatorics · Mathematics 2016-02-08 Jose G. Mijares , Gabriel Padilla

We provide examples of homogeneous spaces which are neither symmetric spaces nor real cohomology spheres, yet have the property that every invariant metric is geometrically formal. We also extend the known obstructions to geometric…

Differential Geometry · Mathematics 2011-01-12 D. Kotschick , S. Terzic

We show that expansive maps from a dense subset of a compact metric space into the metric space itself are isometries

Metric Geometry · Mathematics 2015-07-20 Orest Bucicovschi , David A. Meyer

In a recent paper by a superset of the authors it was proved that for every primitive 3-constrained space $\Gamma$ of finite diameter $\delta$ from Cherlin's catalogue of metrically homogeneous graphs, there exists a finite family $\mathcal…

Combinatorics · Mathematics 2025-11-03 Jan Hubička , Michael Kompatscher , Matěj Konečný

We study manifolds endowed with an (almost) even Clifford (hermitian) structure and admitting a large automorphism group. We classify them when they are simply connected and the dimension of the automorphism group is maximal, and also prove…

Differential Geometry · Mathematics 2016-06-07 Gerardo Arizmendi , Rafael Herrera , Noemi Santana

We provide two novel constructions of $r$ edge-disjoint $K_{k+1}$-free graphs on the same vertex set, each of which has the property that every small induced subgraph contains a complete graph on $k$ vertices. The main novelty of our…

Combinatorics · Mathematics 2025-10-13 Yamaan Attwa , Sam Mattheus , Tibor Szabó , Jacques Verstraete

We study the class of 1-perfectly orientable graphs, that is, graphs having an orientation in which every out-neighborhood induces a tournament. 1-perfectly orientable graphs form a common generalization of chordal graphs and circular arc…

Combinatorics · Mathematics 2016-03-08 Tatiana Romina Hartinger , Martin Milanič

We show that smooth well formed weighted complete intersections have finite automorphism groups, with several obvious exceptions.

Algebraic Geometry · Mathematics 2020-08-13 Victor Przyjalkowski , Constantin Shramov

We study graphs with the property that every edge-colouring admits a monochromatic cycle (the length of which may depend freely on the colouring) and describe those graphs that are minimal with this property. We show that every member in…

Combinatorics · Mathematics 2018-08-01 Damian Reding , Anusch Taraz

For a given graph $F$ we consider the family of (finite) graphs $G$ with the Ramsey property for $F$, that is the set of such graphs $G$ with the property that every two-colouring of the edges of $G$ yields a monochromatic copy of $F$. For…

Combinatorics · Mathematics 2018-02-20 Mathias Schacht , Fabian Schulenburg

Planar locally finite graphs which are almost vertex transitive are discussed. If the graph is 3-connected and has at most one end then the group of automorphisms is a planar discontinuous group and its structure is well-known. A general…

Group Theory · Mathematics 2009-05-08 M. J. Dunwoody

We extend Edmonds' Branching Theorem to locally finite infinite digraphs. As examples of Oxley or Aharoni and Thomassen show, this cannot be done using ordinary arborescences, whose underlying graphs are trees. Instead we introduce the…

Combinatorics · Mathematics 2020-04-06 J. Pascal Gollin , Karl Heuer

We consider a generalisation of the classical Ramsey theory setting to a setting where each of the edges of the underlying host graph is coloured with a {\em set} of colours (instead of just one colour). We give bounds for monochromatic…

Combinatorics · Mathematics 2018-05-30 Sebastián Bustamante , Maya Stein

We study the groups of automorphisms of rational algebraic surfaces that admit a relatively minimal pencil of curves of arithmetic genus one over an algebraically closed field of arbitrary characteristic. In particular, we classify such…

Algebraic Geometry · Mathematics 2021-06-25 Igor Dolgachev , Gebhard Martin

We study the Ramsey property for vector spaces over finite fields with bilinear forms. We prove that symplectic spaces over finite fields do not have the Ramsey property. We also describe vector spaces with skew symmetric bilinear forms and…

Logic · Mathematics 2025-03-12 Aleksander Ivanov , Frédéric Jaffrennou

We prove that posets of bounded height whose cover graphs belong to a fixed class with bounded expansion have bounded dimension. Bounded expansion, introduced by Ne\v{s}et\v{r}il and Ossona de Mendez as a model for sparsity in graphs, is a…

Combinatorics · Mathematics 2019-02-11 Gwenaël Joret , Piotr Micek , Veit Wiechert
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