{ "id": "math/0104194", "version": "v1", "published": "2001-04-19T17:38:05.000Z", "updated": "2001-04-19T17:38:05.000Z", "title": "On the existence of rigid aleph_1-free abelian groups of cardinality aleph_1", "authors": [ "Rüdiger Göbel", "Saharon Shelah" ], "journal": "Abelian Groups and Modules. Proceedings of the Padova Conference, Padova, Italy, 1994. Editors: A. Facchini and C. Menini. Kluwer, New York, 1995, pp 227--237", "categories": [ "math.LO", "math.GR" ], "abstract": "An abelian group is said to be aleph_1-free if all its countable subgroups are free. Our main result is: If R is a ring with R^+ free and |R|