24 citations · 117 across the 105 of their papers we have counts for
8 papers · 2 filters
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…
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…
Banach spaces and groups - order properties and universal models
Saharon Shelah, Alex Usvyatsov
We deal with two natural examples of almost-elementary classes: the class of all Banach spaces (over R or C) and the class of all groups. We show both of these classes do not have…
Subsets of superstable structures are weakly benign
Bektur Baizhanov, John Baldwin, Saharon Shelah
Baizhanov and Baldwin introduced the notion of benign and weakly benign sets to investigate the preservation of stability by naming arbitrary subsets of a stable structure. They co…