857 citations
Counting papers with at most 25 authors, so collaboration author lists do not stand in for the people here.
- Hungarian Academy of SciencesHU402 papers
- Eötvös Loránd UniversityHU156 papers
- Budapest University of Technology and EconomicsHU58 papers
- Central European UniversityAT42 papers
- École Polytechnique Fédérale de LausanneCH31 papers
- Central European University - Budapest Campus24 papers
- University of PannoniaHU23 papers
- Centre National de la Recherche ScientifiqueFR21 papers
- University College LondonGB20 papers
- University of SzegedHU20 papers
- University of Illinois Urbana-ChampaignUS18 papers
- Charles UniversityCZ15 papers
49 papers · 1 filter
Transposition of variables is hard to describe
H. Andréka, I. Németi, Zs. Tuza
The function that interchanges two logical variables in formulas is hard to describe in the following sense. Let denote the Lindenbaum-Tarski formula-algebra of…
Logic families
H. Andréka, Z. Gyenis, I. Németi +1
A logic family is a bunch of logics that belong together in some way. First-order logic is one of the examples. Logics organized into a structure occurs in abstract model theory, i…
Testing definitional equivalence of theories via automorphism groups
H. Andréka, J. Madarász, I. Németi +1
Two first-order logic theories are definitionally equivalent if and only if there is a bijection between their model classes that preserves isomorphisms and ultraproducts (Theorem…
On Erdos--Dushnik--Miller theorem without AC
Amitayu Banerjee, Alexa Gopaulsingh
In set theory without the Axiom of Choice, we study the possible placement of Erdos-Dushnik-Miller theorem restricted to an uncountable set of vertices in the hierarchy of weak cho…
Complexity in the interdefinability of timelike, lightlike and spacelike relatedness of Minkowski spacetime
Hajnal Andréka, Judit X. Madarász, István Németi +1
Interdefinability of timelike, lightlike and spacelike relatedness of Minkowski spacetime is investigated in detail in the paper, with the aim of finding the simplest definitions.…
Two-variable logic has weak, but not strong, Beth definability
H. Andréka, I. Németi
We prove that the two-variable fragment of first-order logic has the weak Beth definability property. This makes the two-variable fragment a natural logic separating the weak and t…
Combinatorial Properties and Dependent choice in symmetric extensions based on Lévy Collapse
Amitayu Banerjee
We work with symmetric extensions based on Lévy Collapse and extend a few results of Arthur Apter. We prove a conjecture of Ioanna Dimitriou from her P.h.d. thesis. We also observe…
Stone type representation theorems via games
Tuğba Aslan, Mohamed Khaled
The classes of relativized relation algebras (whose units are not necessarily transitive as binary relations) are known to be finitely axiomatizable. In this article, we give a new…
Varieties generated by completions
H. Andréka, I. Németi
We prove that persistently finite algebras are not created by completions of algebras, in any ordered discriminator variety. A persistently finite algebra is one without infinite s…
Nonrepresentable relation algebras from group systems
H. Andréka, S. Givant, I. Németi
A series of nonrepresentable relation algebras is constructed from groups. We use them to prove that there are continuum many subvarieties between the variety of representable rela…
The structure of random automorphisms of the rational numbers
Udayan B. Darji, Márton Elekes, Kende Kalina +2
In order to understand the structure of the "typical" element of an automorphism group, one has to study how large the conjugacy classes of the group are. For the case when typical…
A representation theorem for measurable relation algebras
S. Givant, H. Andréka
A relation algebra is called measurable when its identity is the sum of measurable atoms, and an atom is called measurable if its square is the sum of functional elements. In this…
Distances between formal theories
Michèle Friend, Mohamed Khaled, Koen Lefever +1
In the literature, there have been several methods and definitions for working out if two theories are "equivalent" (essentially the same) or not. In this article, we do something…
A representation theorem for measurable relation algebras with cyclic groups
Hajnal Andréka, Steven Givant
A relation algebra is measurable if the identity element is a sum of atoms, and the square x;1;x of each subidentity atom x is a sum of non-zero functional elements. These function…
The variety of coset relation algebras
Steven Givant, Hajnal Andréka
A coset relation algebra is one embeddable into some full coset relation algebra, the latter is an algebra constructed from a system of groups, a coordinated system of isomorphisms…
Coset relation algebras
H. Andréka, S. Givant
A measurable relation algebra is a relation algebra in which the identity element is a sum of atoms that can be measured in the sense that the "size" of each such atom can be defin…
Relation algebras and groups
Steven Givant
Generalizing results of Jónsson and Tarski, Maddux introduced the notion of a pair-dense relation algebra and proved that every pair-dense relation algebra is representable. The no…
Term algebras of elementarily equivalent atom structures
H. Andréka, I. Németi
We exhibit two relation algebra atom structures such that they are elementarily equivalent but their term algebras are not. This answers Problem 14.19 in the book Hirsch, R. and Ho…
On Generalization of Definitional Equivalence to Languages with Non-Disjoint Signatures
Koen Lefever, Gergely Székely
For simplicity, most of the literature introduces the concept of definitional equivalence only to languages with disjoint signatures. In a recent paper, Barrett and Halvorson intro…
The structure of random automorphisms of countable structures
Udayan B. Darji, Márton Elekes, Kende Kalina +2
In order to understand the structure of the `typical' element of an automorphism group, one has to study how large the conjugacy classes of the group are. When typical is meant in…
The structure of random homeomorphisms
Udayan B. Darji, Márton Elekes, Kende Kalina +2
In order to understand the structure of the "typical" element of a homeomorphism group, one has to study how large the conjugacy classes of the group are. When typical means generi…
A game characterizing Baire class 1 functions
Viktor Kiss
Duparc introduced a two-player game for a function between zero-dimensional Polish spaces in which Player II has a winning strategy iff is of Baire class 1. We generalize t…
On Tarski's axiomatic foundations of the calculus of relations
H. Andréka, S. Givant, P. Jipsen +1
It is shown that Tarski's set of ten axioms for the calculus of relations is independent in the sense that no axiom can be derived from the remaining axioms. It is also shown that…
Weak Godel's incompleteness property for some decidable versions of first order logic
Mohamed Khaled
The founding of the theory of cylindric algebras, by Alfred Tarski, was a conscious effort to create algebras out of first order predicate calculus. Let . The classes of non…