Source: J. Symbolic Logic Volume 73, Issue 3
(2008), 765-782.
We use κ-free but not Whitehead Abelian groups to
construct Abstract Elementary Classes (AEC) which satisfy the
amalgamation property but fail various conditions on the locality
of Galois-types. We introduce the notion that an AEC admits
intersections. We conclude that for AEC which admit
intersections, the amalgamation property can have no positive
effect on locality: there is a
transformation of AEC’s which preserves non-locality
but takes any AEC which admits intersections to one with
amalgamation. More specifically we have: Theorem 5.3.
There is an AEC with amalgamation which is not
(ℵ0,ℵ1)-tame but is (2ℵ0,∞)-tame;
Theorem 3.3. It is consistent with ZFC that there is
an AEC with amalgamation which is not (≤ℵ2,≤ℵ2)-compact.
References
J. T. Baldwin, Categoricity, Available at family www.math.uic.edu/\~jbaldwin,200?
J. Baldwin, W. Calvert, J. Goodrick, A. Villaveces, and A. Walczak-Typke, Abelian groups as aec's, preprint,200?
John T. Baldwin and Alexei Kolesnikov, Categoricity, amalgamation, and tameness, preprint: family www.math.uic.edu/\~jbaldwin, to appear in Israel Journal of Mathematics.
J. T. Baldwin, D. W. Kueker, and M. VanDieren, Upward stability transfer theorem for tame abstract elementary classes, Notre Dame Journal of Formal Logic, vol. 47 (2006), pp. 291--298.
P. Eklof and Alan Mekler, Almost free modules: Set theoretic methods, North Holland, 1990.
Rami Grossberg and Alexei Kolesnikov, Excellent abstract elementary classes are tame, preprint.
Rami Grossberg, Classification theory for non-elementary classes, Logic and algebra (Yi Zhang, editor), Contemporary Mathematics 302, AMS, 2002, pp. 165--204.
R. Grossberg and M. VanDieren, Categoricity from one successor cardinal in tame abstract elementary classes, The Journal of Mathematical Logic, vol. 6 (2006), pp. 181--201.
--------, Galois stability for tame abstract elementary classes, Journal of Mathematical Logic, vol. 6 (2006), pp. 1--24.
--------, Shelah's categoricity conjecture from a successor for tame abstract elementary classes, Journal of Symbolic Logic, vol. 71 (2006), pp. 553--568.
T. Hyttinen and M. Kesälä, Independence in finitary abstract elementary classes, Annals of Pure and Applied Logic, vol. 143 (2006), no. 1--3, pp. 103--138.
Olivier Lessmann, Upward categoricity from a successor cardinal for an abstract elementary class with amalgamation, Journal of Symbolic Logic, vol. 70 (2005), pp. 639--661.
Michael Rabin, Classes of structures and sets of sentences with the intersection property, Actes du Colloqe de mathematiques a l'Occasion de Tricentenaire de la mort de B. Pascal, Université de Clermont, 1962, pp. 39--53.
Mathematical Reviews (MathSciNet):
MR284325
S. Shelah, Infinite abelian groups, Whitehead problem and some constructions, Israel Journal of Mathematics, vol. 18 (1974), pp. 243--256.
Mathematical Reviews (MathSciNet):
MR357114
Saharon Shelah, Classification of nonelementary classes II, abstract elementary classes, Classification theory (Chicago, IL, 1985) (J. T. Baldwin, editor), Lecture Notes in Mathematics, vol. 1292, Springer, Berlin, 1987, paper 88: Proceedings of the USA--Israel Conference on Classification Theory, Chicago, December 1985, pp. 419--497.
S. Shelah, Categoricity for abstract classes with amalgamation, Annals of Pure and Applied Logic, vol. 98 (1999), pp. 261--294, paper 394. Consult Shelah for post-publication revisions.
--------, Categoricity of abstract elementary class in two successive cardinals, Israel Journal of Mathematics, vol. 126 (2001), pp. 29--128, paper 576.