53 citations · 306 across the 21 of their papers we have counts for
21 papers
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…
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…
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…
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…
Ultraproducts of continuous posets
H. Andréka, Z. Gyenis, I. Németi
It is known that nontrivial ultraproducts of complete partially ordered sets (posets) are almost never complete. We show that complete additivity of functions is preserved in ultra…