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math.LO2012
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…
math.LO2006
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…
math.LO2004
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…