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We prove that the class of finite two-graphs has the extension property for partial automorphisms (EPPA, or Hrushovski property), thereby answering a question of Macpherson. In other words, we show that the class of graphs has the extension…

组合数学 · 数学 2021-02-24 David Evans , Jan Hubička , Matěj Konečný , Jaroslav Nešetřil

We prove EPPA (extension property for partial automorphisms) for all antipodal classes from Cherlin's list of metrically homogeneous graphs, thereby answering a question of Aranda et al. This paper should be seen as the first application of…

组合数学 · 数学 2021-06-03 Matěj Konečný

We show that every free amalgamation class of finite structures with relations and (symmetric) partial functions is a Ramsey class when enriched by a free linear ordering of vertices. This is a common strengthening of the…

组合数学 · 数学 2021-07-06 David M. Evans , Jan Hubička , Jaroslav Nešetřil

We survey recent developments concerning two properties of classes of finite structures: the Ramsey property and the extension property for partial automorphisms (EPPA).

组合数学 · 数学 2020-10-13 Jan Hubička

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 give strengthened versions of the Herwig-Lascar and Hodkinson-Otto extension theorems for partial automorphisms of finite structures. Such strengthenings yield several combinatorial and group-theoretic consequences for homogeneous…

逻辑 · 数学 2019-04-17 Daoud Siniora , Sławomir Solecki

A class K of finite structures is said to have the extension property for automorphisms (EP) if for every A in K there exists an extension B in K such that every partial isomorphism on the structure A extends to an automorphism of B.…

逻辑 · 数学 2008-02-03 Bernhard Herwig

We prove that for every $n\geq 2$ the class of all finite $n$-partite tournaments (orientations of complete $n$-partite graphs) has the extension property for partial automorphisms, that is, for every finite $n$-partite tournament $G$ there…

组合数学 · 数学 2019-03-19 Jan Hubička , Colin Jahel , Matěj Konečný , Marcin Sabok

We present a proof of the extension property for partial automorphisms (EPPA) for classes of finite $n$-partite tournaments for $n \in \{2,3,\ldots,\omega\}$, and for the class of finite semigeneric tournaments. We also prove that the…

组合数学 · 数学 2025-10-01 Jan Hubička , Colin Jahel , Matěj Konečný , Marcin Sabok

The structural Ramsey theory is a field on the boundary of combinatorics and model theory with deep connections to topological dynamics. Most of the known Ramsey classes in finite binary symmetric relational language can be shown to be…

组合数学 · 数学 2019-08-13 Matěj Konečný

If $G$ is a graph, $A$ and $B$ its induced subgraphs, and $f\colon A\to B$ an isomorphism, we say that $f$ is a \emph{partial automorphism} of $G$. In 1992, Hrushovski proved that graphs have the \emph{extension property for partial…

组合数学 · 数学 2025-10-01 David Bradley-Williams , Peter J. Cameron , Jan Hubička , Matěj Konečný

In this paper we consider the classes of all continuous $\mathcal{L}$-(pre-)structures for a continuous first-order signature $\mathcal{L}$. We characterize the moduli of continuity for which the classes of finite, countable, or all…

逻辑 · 数学 2026-02-11 Su Gao , Xuanzhi Ren

In this paper we study a notion of HL-extension (HL standing for Herwig--Lascar) for a structure in a finite relational language $\mathcal{L}$. We give a description of all finite minimal HL-extensions of a given finite…

逻辑 · 数学 2020-07-22 Mahmood Etedadialiabadi , Su Gao

We prove the Ramsey property for classes of ordered structures with closures and given local properties. This generalises earlier results: the Ne\v{s}et\v{r}il-R\"odl Theorem, the Ramsey property of partial orders and metric spaces as well…

组合数学 · 数学 2019-09-04 Jan Hubička , Jaroslav Nešetřil

We state the Ramsey property of classes of ordered structures with closures and given local properties. This generalises many old and new results: the Ne\v{s}et\v{r}il-R\"{o}dl Theorem, the author's Ramsey lift of bowtie-free graphs as well…

组合数学 · 数学 2017-06-07 Jan Hubička , Jaroslav Nešetřil

We derive a new sufficient condition for the existence of {\omega}-categorical universal structures in classes of relational structures with constraints, augmenting results by Cherlin, Shelah, Chi, and Hubi\v{c}ka and Ne\v{s}et\v{r}il.…

逻辑 · 数学 2012-03-29 Christian Pech , Maja Pech

We generalize to the setting of Arveson's maximal subdiagonal subalgebras of finite von Neumann algebras, the Szeg\"o $L^p$-distance estimate, and classical theorems of F. and M. Riesz, Gleason and Whitney, and Kolmogorov. In so doing, we…

算子代数 · 数学 2007-05-23 David P. Blecher , Louis E. Labuschagne

We investigate a generalization of the {\L}o\'s-Tarski preservation theorem via the semantic notion of \emph{preservation under substructures modulo $k$-sized cores}. It was shown earlier that over arbitrary structures, this semantic notion…

计算机科学中的逻辑 · 计算机科学 2014-01-24 Abhisekh Sankaran , Bharat Adsul , Supratik Chakraborty

Given two Fra\"iss\'e-like classes with generic limits, we ask whether we can merge the two classes into one class with a generic limit. We study the properties of these merges and their generics, as well as their connections to structural…

逻辑 · 数学 2024-11-19 Morgan Bryant

We study the problem of extending partial isomorphisms for hypertournaments, which are relational structures generalizing tournaments. This is a generalized version of an old question of Herwig and Lascar. We show that the generalized…

逻辑 · 数学 2018-09-19 Jingyin Huang , Michael Pawliuk , Marcin Sabok , Daniel Wise
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