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We develop a transfer principle of structural Ramsey theory from finite structures to ultraproducts. We show that under certain mild conditions, when a class of finite structures has finite small Ramsey degrees, under the (Generalized)…

Logic · Mathematics 2025-12-03 Dana Bartošová , Mirna Džamonja , Rehana Patel , Lynn Scow

We consider limit probabilities of first order properties in random graphs with a given degree sequence. Under mild conditions on the degree sequence, we show that the closure set of limit probabilities is a finite union of closed…

Combinatorics · Mathematics 2024-05-24 Alberto Larrauri , Guillem Perarnau

We present a short and self-contained proof of the extension property for partial isometries of the class of all finite metric spaces.

Combinatorics · Mathematics 2025-10-01 Jan Hubička , Matěj Konečný , Jaroslav Nešetřil

We define toric partial orders, corresponding to regions of graphic toric hyperplane arrangements, just as ordinary partial orders correspond to regions of graphic hyperplane arrangements. Combinatorially, toric posets correspond to finite…

Combinatorics · Mathematics 2012-11-20 Mike Develin , Matthew Macauley , Victor Reiner

In this paper we consider big Ramsey degrees of finite chains in countable ordinals. We prove that a countable ordinal has finite big Ramsey degrees if and only if it is smaller than $\omega^\omega$. Big Ramsey degrees of finite chains in…

Combinatorics · Mathematics 2019-07-29 Dragan Mašulović , Branislav Šobot

We show that canonical Ramsey numbers for partite hypergraphs grow single exponentially for any fixed uniformity.

Combinatorics · Mathematics 2024-11-26 Matías Azócar Carvajal , Giovanne Santos , Mathias Schacht

We give a new proof of the fact that finite bipartite graphs cannot be axiomatized by finitely many first-order sentences among FINITE graphs. (This fact is a consequence of a general theorem proved by L. Ham and M. Jackson, and the…

Logic · Mathematics 2021-04-01 Gábor Czédli

We show that the Ramsey number is linear for every uniform hypergraph with bounded-degree. This is a hypergraph extension of the famous theorem for ordinary graphs which Chv\'atal et al. showed in 1983. Our proof is simple, contains the…

Combinatorics · Mathematics 2007-12-14 Yoshiyasu Ishigami

We prove that the theory of the Farey graph is pseudofinite by constructing a sequence of finite structures that satisfy increasingly large subsets of its first-order axiomatization. This graph is an important object in the study of curve…

Logic · Mathematics 2026-03-26 Connor Martinez Lockhart

The paper examines a partial order on bipartite graphs (X1, X2, E) with n vertices, X1UX2={1,2,...,n}. This partial order is a natural partial order of subobjects of an object in a triangular category with bipartite graphs as morphisms.

Discrete Mathematics · Computer Science 2009-06-05 Emil Daniel Schwab

We determine, up to the equivalence of first-order interdefinability, all structures which are first-order definable in the random partial order. It turns out that these structures fall into precisely five equivalence classes. We achieve…

Ramsey algebras are algebras that induce Ramsey spaces, which are generalizations of the Ellentuck space and Milliken's space. Previous work suggests a possible local version of Ramsey algebras induced by infinite sequences. Hence, we…

Logic · Mathematics 2017-04-13 Wen Chean Teh , Zu Yao Teoh

The Ramsey's theorem says that a graph with sufficiently many vertices contains a clique or stable set with many vertices. Now we attach some parameter to every vertex, such as degree. Consider the case a graph with sufficiently many…

Combinatorics · Mathematics 2023-07-18 Jin Sun

We define a fragment of monadic infinitary second-order logic corresponding to an abstract separation property. We use this to define the concept of a separation subclass. We use model theoretic techniques and games to show that separation…

Logic · Mathematics 2021-12-09 Rob Egrot

As a result of 33 intercontinental Zoom calls, we characterise big Ramsey degrees of the generic partial order in a similar way as Devlin characterised big Ramsey degrees of the generic linear order (the order of rationals).

We give Ramsey expansions of classes of generalised metric spaces where distances come from a linearly ordered commutative monoid. This complements results of Conant about the extension property for partial automorphisms and extends an…

Combinatorics · Mathematics 2021-07-06 Jan Hubička , Matěj Konečný , Jaroslav Nešetřil

We prove several results from different areas of extremal combinatorics, giving complete or partial solutions to a number of open problems. These results, coming from areas such as extremal graph theory, Ramsey theory and additive…

Combinatorics · Mathematics 2013-08-26 David Conlon , Jacob Fox , Benny Sudakov

We show that the universal homogeneous partial order has finite big Ramsey degrees and discuss several corollaries. Our proof relies on parameter spaces and the Carlson-Simpson theorem rather than on (a strengthening of) the…

Combinatorics · Mathematics 2025-06-09 Jan Hubička

In 2012 M. Soki\'c proved that the class of all finite permutations has the Ramsey property. Using different strategies the same result was then reproved in 2013 by J. B\"ottcher and J. Foniok, in 2014 by M. Bodirsky and in 2015 yet another…

Combinatorics · Mathematics 2017-10-31 Dragan Masulovic

The problem of classifying equivalence classes of presentations up to isomorphism of Cayley graphs is considered in this article in the case of dicyclic groups. The number of equivalence classes of presentations is uniformly bounded - it is…

Group Theory · Mathematics 2019-03-18 Peteris Daugulis