5 papers
On Induced Subgraphs of Finite Graphs not Containing Large Empty and Complete Subgraphs
Gábor Sági
In their celebrated paper [Ramsey-Type Theorems, Discrete Appl. Math. 25 (1989) 37-52], Erdős and Hajnal asked the following: is it true, that for any finite graph H there exists a…
Clones above the unary clone
Martin Goldstern, Gábor Sági, Saharon Shelah
Let c be the cardinality of the continuum. We give a family of pairwise incomparable clones (on a countable base set) 2^c members, all with the same unary fragment, namely the set…
On Weak and Strong Interpolation in Algebraic Logics
Gabor Sagi, Saharon Shelah
We show that there is a restriction, or modification of the finite-variable fragments of First Order Logic in which a weak form of Craig's Interpolation Theorem holds, but a strong…
Representation of ideals of relational structures
C. Delhomme, M. Pouzet, G. Sagi +1
The \textit{age} of a relational structure of signature is the set of its finite induced substructures, considered up to isomorphism. This is a…
On topological properties of ultraproducts of finite sets
Gabor Sagi, Saharon Shelah
Motivated by the model theory of higher order logics, a certain kind of topological spaces had been introduced on ultraproducts. These spaces are called ultratopologies. Ultratopol…