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( Automorphisms, homomorphisms, endomorphisms, etc. )
1. CJM 2003 (vol 55 pp. 750)
 Göbel, Rüdiger; Shelah, Saharon; Strüngmann, Lutz

AlmostFree $E$Rings of Cardinality $\aleph_1$
An $E$ring is a unital ring $R$ such that every endomorphism of
the underlying abelian group $R^+$ is multiplication by some
ring element. The existence of almostfree $E$rings of
cardinality greater than $2^{\aleph_0}$ is undecidable in $\ZFC$.
While they exist in G\"odel's universe, they do not exist in other
models of set theory. For a regular cardinal $\aleph_1 \leq
\lambda \leq 2^{\aleph_0}$ we construct $E$rings of cardinality
$\lambda$ in $\ZFC$ which have $\aleph_1$free additive structure.
For $\lambda=\aleph_1$ we therefore obtain the existence of
almostfree $E$rings of cardinality $\aleph_1$ in $\ZFC$.
Keywords:$E$rings, almostfree modules Categories:20K20, 20K30, 13B10, 13B25 

2. CJM 1998 (vol 50 pp. 719)
 Göbel, Rüdiger; Shelah, Saharon

Indecomposable almost free modulesthe local case
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 rank $\aleph_1$
with endomorphism algebra End$_RG = A$. Clearly the result does not
hold for fields. Recall that an $R$module is $\aleph_1$free if all
its countable submodules are free, a condition closely related to
Pontryagin's theorem. This result has many consequences, depending on
the algebra $A$ in use. For instance, if we choose $A = R$, then
clearly $G$ is an indecomposable `almost free' module. The existence of
such modules was unknown for rings with only finitely many primes like
$R = \hbox{\Bbbvii Z}_{(p)}$, the integers localized at some prime $p$. The result
complements a classical realization theorem of Corner's showing that
any such algebra is an endomorphism algebra of some torsionfree,
reduced $R$module $G$ of countable rank. Its proof is based on new
combinatorialalgebraic techniques related with what we call {\it rigid
treeelements\/} coming from a module generated over a forest of trees.
Keywords:indecomposable modules of local rings, $\aleph_1$free modules of rank $\aleph_1$, realizing rings as endomorphism rings Categories:20K20, 20K26, 20K30, 13C10 
