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We represent the universal Menger curve as the topological realization $|\mathbb{M}|$ of the projective Fra\"iss\'e limit ${\mathbb M}$ of the class of all finite connected graphs. We show that $\mathbb{M}$ satisfies combinatorial analogues…

Logic · Mathematics 2020-01-07 Aristotelis Panagiotopoulos , Slawomir Solecki

We investigate Ramsey expansions, the coherent extension property for partial isometries (EPPA), and the existence of a stationary independence relation for all classes of metrically homogeneous graphs from Cherlin's catalogue. We show…

We study Gibbs partitions that typically form a unique giant component. The remainder is shown to converge in total variation toward a Boltzmann-distributed limit structure. We demon- strate how this setting encompasses arbitrary weighted…

Combinatorics · Mathematics 2016-12-15 Benedikt Stufler

We present a refinement of Ramsey numbers by considering graphs with a partial ordering on their vertices. This is a natural extension of the ordered Ramsey numbers. We formalize situations in which we can use arbitrary families of…

Combinatorics · Mathematics 2016-11-29 Christopher Cox , Derrick Stolee

The $s$-colour size-Ramsey number of a hypergraph $H$ is the minimum number of edges in a hypergraph $G$ whose every $s$-edge-colouring contains a monochromatic copy of $H$. We show that the $s$-colour size-Ramsey number of the $t$-power of…

Combinatorics · Mathematics 2021-04-19 Shoham Letzter , Alexey Pokrovskiy , Liana Yepremyan

We present recent advances in harmonic analysis on infinite graphs. Our approach combines combinatorial tools with new results from the theory of unbounded Hermitian operators in Hilbert space, geometry, boundary constructions, and spectral…

Combinatorics · Mathematics 2020-10-26 Sergey Bezuglyi , Palle E. T. Jorgensen

Our work builds on known results for k-uniform hypergraphs including the existence of limits, a Regularity Lemma and a Removal Lemma. Our main tool here is a theory of measures on ultraproduct spaces which establishes a correspondence…

Logic · Mathematics 2014-12-30 Ashwini Aroskar , James Cummings

We show the density theorem for the class of finite oriented trees ordered by the homomorphism order. We also show that every interval of oriented trees, in addition to be dense, is in fact universal. We end by considering the fractal…

Combinatorics · Mathematics 2019-06-11 Jan Hubička , Jaroslav Nešetřil , Pablo Oviedo

We present a unified approach to proving Ramsey-type theorems for graphs with a forbidden induced subgraph which can be used to extend and improve the earlier results of Rodl, Erdos-Hajnal, Promel-Rodl, Nikiforov, Chung-Graham, and…

Combinatorics · Mathematics 2007-12-27 Jacob Fox , Benny Sudakov

We characterize the strength, in terms of Weihrauch degrees, of certain problems related to Ramsey-like theorems concerning colourings of the rationals and of the natural numbers. The theorems we are chiefly interested in assert the…

Logic in Computer Science · Computer Science 2023-12-05 Arno Pauly , Cécilia Pradic , Giovanni Solda

We discuss in the context of finite extensions two classical theorems of Takahasi and Howson on subgroups of free groups. We provide bounds for the rank of the intersection of subgroups within classes of groups such as virtually free…

Group Theory · Mathematics 2014-12-11 Vitor Araujo , Pedro V. Silva , Mihalis Sykiotis

The celebrated Erd\H{o}s-Hajnal Conjecture says that in any proper hereditary class of finite graphs we are guaranteed to have a clique or anti-clique of size $n^c$, which is a much better bound than the logarithmic size that is provided by…

Combinatorics · Mathematics 2022-09-20 Leonardo N. Coregliano , Maryanthe Malliaris

The study of upper density problems on Ramsey theory was initiated by Erd\H{o}s and Galvin in 1993. In this paper we are concerned with the following problem: given a fixed finite graph $F$, what is the largest value of $\lambda$ such that…

Combinatorics · Mathematics 2020-10-27 József Balogh , Ander Lamaison

I will give a presentation of an abstract approach to finite Ramsey theory found in an earlier paper of mine. I will prove from it a common generalization of Deuber's Ramsey theorem for regular trees and a recent Ramsey theorem of Jasinski…

Combinatorics · Mathematics 2012-10-03 Slawomir Solecki

We study a natural generalization of inverse systems of finite regular covering spaces. A limit of such a system is a fibration whose fibres are profinite topological groups. However, as shown in a previous paper (Conner-Herfort-Pavesic:…

Algebraic Topology · Mathematics 2019-01-09 Gregory R. Conner , Wolfgang Herfort , Petar Pavešić

We characterize the computational content and the proof-theoretic strength of a Ramsey-type theorem for bi-colorings of so-called {\em exactly large} sets. An {\it exactly large} set is a set $X\subset\Nat$ such that $\card(X)=\min(X)+1$.…

Logic · Mathematics 2024-01-10 Lorenzo Carlucci , Konrad Zdanowski

This paper is the fourth and the last part of the series "Spherical higher order Fourier analysis over finite fields", aiming to develop the higher order Fourier analysis method along spheres over finite fields, and to solve the Geometric…

Number Theory · Mathematics 2024-07-29 Wenbo Sun

We investigate the behavior of countable Borel equivalence relations (CBERs) on topological Ramsey spaces. First, we give a simple proof of the fact that every CBER on $[\mathbb{N}]^{\mathbb{N}}$ is hyperfinite on some set of the form…

Logic · Mathematics 2026-02-10 Balázs Bursics , Zoltán Vidnyánszky

Using recent work by Erman-Sam-Snowden, we show that finitely generated ideals in the ring of bounded-degree formal power series in infinitely many variables have finitely generated Gr\"obner bases relative to the graded reverse…

Commutative Algebra · Mathematics 2021-04-06 Jan Draisma , Michal Lason , Anton Leykin

Finite topological spaces are in bijective correspondence with preorders on finite sets. We undertake their study using combinatorial tools that have been developed to investigate general discrete structures. A particular emphasis will be…

Algebraic Topology · Mathematics 2015-09-04 Loïc Foissy , Claudia Malvenuto , Frédéric Patras
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