324 citations · 1.7k across the 753 of their papers we have counts for
10 papers · 2 filters
A definable nonstandard model of the reals
Vladimir Kanovei, Saharon Shelah
We prove in ZFC the existence of a definable, countably saturated elementary extension of the reals. It seems that it has been taken for granted that there is no distinguished, def…
There may be no Hausdorff ultrafilters
Tomek Bartoszynski, Saharon Shelah
An ultrafilter U is Hausdorff if for any two functions f,g mapping N to N, f(U)=g(U) iff f(n)=g(n) for n in some X in U. We will show that it is consistent that there are no Hausdo…
Automorphisms and strongly invariant relations
Ferdinand Börner, Martin Goldstern, Saharon Shelah
We investigate characterizations of the Galois connection sInv-Aut between sets of finitary relations on a base set A and their automorphisms. In particular, for A=omega_1, we cons…
Critical cardinalities and additivity properties of combinatorial notions of smallness
Saharon Shelah, Boaz Tsaban
Motivated by the minimal tower problem, an earlier work studied diagonalizations of covers where the covers are related to linear quasiorders (tau-covers). We deal with two types o…
Karp complexity and classes with the independence property
Michael C. Laskowski, Saharon Shelah
A class K of structures is controlled if for all cardinals lambda, the relation of L_{infty,lambda}-equivalence partitions K into a set of equivalence classes (as opposed to a prop…
The structure of Ext(A,Z) and GCH: possible co-Moore spaces
Paul C. Eklof, Saharon Shelah
We consider what Ext(A,Z) can be when A is torsion-free and Hom(A,Z)=0. We thereby give an answer to a question of Golasinski and Goncalves which asks for the divisible Abelian gro…