15 citations · 60 across the 67 of their papers we have counts for
10 papers · 1 filter
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…
Asymptotic cones of finitely presented groups
Linus Kramer, Saharon Shelah, Katrin Tent +1
Let G be a connected semisimple Lie group with at least one absolutely simple factor S such that R-rank(S) is at least 2, and let be a uniform lattice in G. (a) If holds,…
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…