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We give an almost entirely model-theoretic account of both Ramsey classes of finite structures and of generalized indiscernibles as studied in special cases in (for example) [7], [9]. We understand "theories of indiscernibles" to be special…

Logic · Mathematics 2012-10-30 Cameron Donnay Hill

Building off of recent results on Keisler's order, we show that consistently, $\leq_{SP}$ has infinitely many classes. In particular, we define the property of $\leq k$-type amalgamation for simple theories, for each $2 \leq k < \omega$. If…

Logic · Mathematics 2024-09-24 Saharon Shelah , Danielle Ulrich

In the article at hand, we sketch how, by utilizing nilpotency to its fullest extent (Engel, Super Engel) while using methods from the theory of universal enveloping algebras, a complete description of the indecomposable representations may…

Representation Theory · Mathematics 2012-10-09 Hans Plesner Jakobsen

Let $G$ be a closed highly homogeneous subgroup of $S_{\infty}$ not involving circular orderings. We show that the closure of a conjugacy class from $G$ contains a conjugacy class which is comeagre in it. Furthermore, we show that the…

Logic · Mathematics 2025-04-23 Monika Drzewiecka , Aleksander Ivanov , Bartosz Mokry

We extend the concept of "almost indiscernible theory" introduced by Pillay and Sklinos in [Bull. Symb. Log., 2015] (which was itself a modernization and expansion of Baldwin and Shelah [Algebra Universalis, 1983]), to uncountable languages…

Logic · Mathematics 2022-01-14 T. G. Kucera , Anand Pillay

The tangled closure of a collection of subsets of a topological space is the largest subset in which each member of the collection is dense. This operation models a logical `tangle modality' connective, of significance in finite model…

Logic · Mathematics 2018-11-08 Robert Goldblatt , Ian Hodkinson

We show that certain classes of modules have universal models with respect to pure embeddings. $Theorem.$ Let $R$ be a ring, $T$ a first-order theory with an infinite model extending the theory of $R$-modules and $K^T=(Mod(T), \leq_{pp})$…

Logic · Mathematics 2020-02-24 Thomas G. Kucera , Marcos Mazari-Armida

The categoricity spectrum of a class of structures is the collection of cardinals in which the class has a single model up to isomorphism. Assuming that cardinal exponentiation is injective (a weakening of the generalized continuum…

Logic · Mathematics 2019-10-03 Sebastien Vasey

We characterize completey (give a necessary and suffcient condition using special neat embeddings)for a relation algebra to belong to the amalgamation, strong amalgamation, and superamalgamation base of the class of representable algebras.…

Logic · Mathematics 2013-04-03 Tarek Sayed Ahmed

Generalised indiscernibles highlight a strong link between model theory and structural Ramsey theory. In this paper, we use generalised indiscernibles as tools to prove results in both these areas. More precisely, we first show that a…

Logic · Mathematics 2024-08-13 Nadav Meir , Aris Papadopoulos , Pierre Touchard

We introduce special classes of irreducible representations of groups: thick representations and dense representations. Denseness implies thickness, and thickness implies irreducibility. We show that absolute thickness and absolute…

Algebraic Geometry · Mathematics 2019-05-10 Kazunori Nakamoto , Yasuhiro Omoda

Let K be an abstract elementary class satisfying the joint embedding and the amalgamation properties. Let m be a cardinal above the the L\"owenheim-Skolem number of the class. Suppose K satisfies the disjoint amalgamation property for limit…

Logic · Mathematics 2015-02-09 R. Grossberg , M. VanDieren , A. Villaveces

We provide a self-contained introduction to the classical theory of universal-homogeneous models (also known as generic structures, rich models, or Fra\"iss\'e limits). In the literature, most treatments restrict consideration to embeddings…

Logic · Mathematics 2010-09-10 Silvia Barbina , Domenico Zambella

We classify essential algebras whose irredundant non-refinable covers consist of primal algebras. The proof is obtained by constructing one to one correspondence between such algebras and partial orders on finite sets. Further, we prove…

Logic · Mathematics 2014-06-26 Shohei Izawa

A few steps are made towards representation theory of embeddability among uncountable graphs. A monotone class of graphs is defined by forbidding countable subgraphs, related to the graph's end-structure. Using a combinatorial theorem of…

Logic · Mathematics 2016-09-06 Menachem Kojman

Theories of classification distinguish classes with some good structure theorem from those for which none is possible. Some classes (dense linear orders, for instance) are non-classifiable in general, but are classifiable when we consider…

Logic · Mathematics 2007-05-23 Wesley Calvert

The goal of this work is to prove an embedding theorem for compact almost complex manifolds into complex algebraic varieties. It is shown that every almost complex structure can be realized by the transverse structure to an algebraic…

Complex Variables · Mathematics 2016-07-18 Jean-Pierre Demailly , Hervé Gaussier

A module is called absolutely indecomposable if it is directly indecomposable in every generic extension of the universe. We want to show the existence of large abelian groups that are absolutely indecomposable. This will follow from a more…

Logic · Mathematics 2007-11-21 Rüdiger Göbel , Saharon Shelah

The geometric and algebraic theory of monomial ideals and multigraded modules is initiated over real-exponent polynomial rings and, more generally, monoid algebras for real polyhedral cones. The main results include the generalization of…

Commutative Algebra · Mathematics 2025-11-11 Ezra Miller

Deciding the amalgamation property for a given class of finite structures is an important subroutine in classifying countable finitely homogeneous structures. We study the computational complexity of the amalgamation decision problem for…

Logic in Computer Science · Computer Science 2025-09-03 Jakub Rydval
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