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An infinite graph is highly connected if the complement of any subgraph of smaller size is connected. We consider weaker versions of Ramsey's Theorem asserting that in any coloring of the edges of a complete graph there exist large highly…

Logic · Mathematics 2018-12-18 Jeffrey Bergfalk , Michael Hrušák , Saharon Shelah

In this paper we investigate algebraic properties of big Ramsey degrees in categories satisfying some mild conditions. As the first nontrivial consequence of the generalization we advocate in this paper we prove that small Ramsey degrees…

Combinatorics · Mathematics 2025-11-27 Dragan Mašulović

We present three examples of countable homogeneous structures (also called Fraisse limits) whose automorphism groups are not universal, namely, fail to contain isomorphic copies of all automorphism groups of their substructures. Our first…

Group Theory · Mathematics 2021-08-25 W. Kubis , S. Shelah

We prove a selection of results from different areas of extremal combinatorics, including complete or partial solutions to a number of open problems. These results, coming mainly from extremal graph theory and Ramsey theory, have been…

Combinatorics · Mathematics 2020-08-11 David Conlon , Jacob Fox , Benny Sudakov

In previous papers, threshold probabilities for the properties of a random distance graph to contain strictly balanced graphs were found. We extend this result to arbitrary graphs and prove that the number of copies of a strictly balanced…

Combinatorics · Mathematics 2018-05-09 A. V. Burkin , M. E. Zhukovskii

We show that minimal length carrier graphs are not unique, but if M is in a large class of hyperbolic 3-manifolds, including the geometrically finite ones, then M has only finitely many minimal length carrier graphs and no two of them are…

Geometric Topology · Mathematics 2013-06-25 Michael Siler

The classical Ramsey theorem, states that every graph contains either a large clique or a large independent set. Here we investigate similar dichotomic phenomena in the context of finite metric spaces. Namely, we prove statements of the…

Combinatorics · Mathematics 2007-05-23 Yair Bartal , Nathan Linial , Manor Mendel , Assaf Naor

We introduce and study asymptotically rigid mapping class groups of certain infinite graphs. We determine their finiteness properties and show that these depend on the number of ends of the underlying graph. In a special case where the…

Geometric Topology · Mathematics 2025-09-01 Thomas Hill , Sanghoon Kwak , Brian Udall , Jeremy West

We study the automorphism group of graphons (graph limits). We prove that after an appropriate "standardization" of the graphon, the automorphism group is compact. Furthermore, we characterize the orbits of the automorphism group on…

Combinatorics · Mathematics 2021-02-17 László Lovász , Balázs Szegedy

In this paper we study the one dimensional random geometric graph when the location of the nodes are independent and exponentially distributed. We derive exact results and the limit theorems for the connectivity and other properties…

Probability · Mathematics 2007-05-23 Bhupendra Gupta , Srikanth K. Iyer , D. Manjunath

The main result provide a common generalization for Ramsey-type theorems concerning finite colorings of edge sets of complete graphs with vertices in infinite semigroups. We capture the essence of theorems proved in different fields: for…

Combinatorics · Mathematics 2021-07-08 Piotr Szewczak

When dealing with symmetry properties of mathematical objects, one of the fundamental questions is to determine their full automorphism group. In this paper this question is considered in the context of even/odd permutations dichotomy. More…

Combinatorics · Mathematics 2016-08-30 Klavdija Kutnar , Dragan Marusic

Chv\'atal, R\"odl, Szemer\'edi and Trotter proved that the Ramsey numbers of graphs of bounded maximum degree are linear in their order. We prove that the same holds for 3-uniform hypergraphs. The main new tool which we prove and use is an…

Combinatorics · Mathematics 2007-05-23 Oliver Cooley , Nikolaos Fountoulakis , Daniela Kühn , Deryk Osthus

Conventional Ramsey-theoretic investigations for edge-colourings of complete graphs are framed around avoidance of certain configurations. Motivated by considerations arising in the field of Qualitative Reasoning, we explore edge colourings…

Combinatorics · Mathematics 2022-01-11 Badriah Al Juaid , Marcel Jackson , James Koussas , Tomasz Kowalski

The purpose of this survey is to provide a gentle introduction to several recent breakthroughs in graph Ramsey theory. In particular, we will outline the proofs (due to various groups of authors) of exponential improvements to the diagonal,…

Combinatorics · Mathematics 2026-01-09 Robert Morris

In this paper, we present several density-type theorems which show how to find a copy of a sparse bipartite graph in a graph of positive density. Our results imply several new bounds for classical problems in graph Ramsey theory and improve…

Combinatorics · Mathematics 2007-11-12 Jacob Fox , Benny Sudakov

We prove an infinite Ramsey theorem for noncommutative graphs realized as unital self-adjoint subspaces of linear operators acting on an infinite dimensional Hilbert space. Specifically, we prove that if V is such a subspace, then provided…

Operator Algebras · Mathematics 2017-11-28 Matthew Kennedy , Taras Kolomatski , Daniel Spivak

We define a solvable extension of the graph 2-step nilpotent Lie algebras of [5] by adding elements corresponding to the 3-cliques of the graph. We study some of their basic properties and we prove that two such Lie algebras are isomorphic…

Rings and Algebras · Mathematics 2017-09-21 Gueo Grantcharov , Vladimir Grantcharov , Plamen Iliev

We consider non-trivial homomorphisms to reflexive oriented graphs in which some pair of adjacent vertices have the same image. Using a notion of convexity for oriented graphs, we study those oriented graphs that do not admit such…

Discrete Mathematics · Computer Science 2023-06-22 Christopher Duffy , Sonja Linghui Shan

Homomorphically full graphs are those for which every homomorphic image is isomorphic to a subgraph. We extend the definition of homomorphically full to oriented graphs in two different ways. For the first of these, we show that…

Discrete Mathematics · Computer Science 2024-02-14 Thomas Bellitto , Christopher Duffy , Gary MacGillivray