6 papers
On Crawley Modules
Rüdiger Göbel, Saharon Shelah
This continues recent work in a paper by Corner, Gobel and Goldsmith. A particular question was left open: Is it possible to carry over the results concerning the undecidability of…
Characterizing automorphism groups of ordered abelian groups
Rüdiger Göbel, Saharon Shelah
We characterize the groups isomorphic to full automorphism groups of ordered abelian groups. The result will follow from classical theorems on ordered groups adding an argument fro…
Indecomposable almost free modules - the local case
Rüdiger Göbel, Saharon Shelah
Let R be a countable, principal ideal domain which is not a field and A be a countable R-algebra which is free as an R-module. Then we will construct an aleph_1-free R-module G of…
Groups isomorphic to all their non-trivial normal subgroups
Rüdiger Göbel, Agnes T. Paras, Saharon Shelah
In answer to a question of P. Hall, we supply another construction of a group which is isomorphic to each of its non-trivial normal subgroups.
Decompositions of Reflexive Modules
Ruediger Goebel, Saharon Shelah
We continue [GbSh:568] (math.LO/0003164), proving a stronger result under the special continuum hypothesis (CH). The original question of Eklof and Mekler related to dual abelian g…
Some Nasty Reflexive Groups
Ruediger Goebel, Saharon Shelah
In "Almost Free Modules, Set-theoretic Methods", Eklof and Mekler raised the question about the existence of dual abelian groups G which are not isomorphic to Z+G. Recall that G is…