Abstract
We show, assuming a mild set-theoretic hypothesis, that if an abstract elementary class (AEC) has a superstable-like forking notion for models of cardinality λ and a superstable-like forking notion for models of cardinality λ+, then orbital types over models of cardinality λ+ are determined by their restrictions to submodels of cardinality λ. By a superstable-like forking notion, we mean here a good frame, a central concept of Shelah’s book on AECs.
It is known that locality of orbital types together with the existence of a superstable-like notion for models of cardinality λ implies the existence of a superstable-like notion for models of cardinality λ+, and here we prove the converse. An immediate consequence is that forking in λ+ can be described in terms of forking in λ.
Similar content being viewed by others
References
J. T. Baldwin, Strong saturation and the foundations of stability theory, in Logic Colloquium’ 82 (Florence, 1982), Studies in Logic and the Foundations of Mathematics, Vol. 112, North-Holland, Amsterdam, 1984, pp. 71–84.
J. T. Baldwin, Categoricity, University Lecture Series, Vol. 50, American Mathematical Society, Providence, RI, 2009.
W. Boney, Tameness and extending frames, Journal of Mathematical Logic 14 2014, 1450007.
W. Boney, Tameness from large cardinal axioms, Journal of Symbolic Logic 79 2014, 1092–1119.
W. Boney and S. Unger, Large cardinal axioms from tameness in AECs, Proceedings of the American Mathematical Society 145 2017, 4517–4532.
W. Boney and S. Vasey, A survey on tame abstract elementary classes, in Beyond First Order Model Theory, CRC Press, Boca Raton, FL, 2017, pp. 353–427.
W. Boney and S. Vasey, Tameness and frames revisited, Journal of Symbolic Logic 82 2017, 995–1021.
W. Boney and S. Vasey, Good frames in the Hart-Shelah example, Archive for Mathematical Logic 57 2018, 687–712.
R. Grossberg and A. Kolesnikov, Excellent abstract elementary classes are tame, http://www.math.cmu.edu/~rami/AtameP.pdf.
R. Grossberg and M. VanDieren, Categoricity from one successor cardinal in tame abstract elementary classes, Journal of Mathematical Logic 6 2006, 181–201.
R. Grossberg and M. VanDieren, Galois-stability for tame abstract elementary classes, Journal of Mathematical Logic 6 2006, 25–49.
R. Grossberg and M. VanDieren, Shelah’s categoricity conjecture from a successor for tame abstract elementary classes, Journal of Symbolic Logic 71 2006, 553–568.
R. Grossberg, M. VanDieren and A. Villaveces, Uniqueness of limit models in classes with amalgamation, Mathematical Logic Quarterly 62 2016, 367–382.
B. Hart and S. Shelah, Categoricity over P for first order T or categoricity for ϕ ∈ Lω1, ωcan stop at \({\aleph _k}\)while holding for \({\aleph _0},\, \ldots ,\,{\aleph _{k - 1}}\), Israel Journal of Mathematics 70 (1990), 219–235.
A. Jarden, Tameness, uniqueness triples, and amalgamation, Annals of Pure and Applied Logic 167 2016, 155–188.
A. Jarden and S. Shelah, Non forking good frames without local character, http://arxiv.org/abs/1105.3674v1.
A. Jarden and S. Shelah, Non-forking frames in abstract elementary classes, Annals of Pure and Applied Logic 164 2013, 135–191.
M. Makkai and S. Shelah, Categoricity of theories in Lκ,ω, with κ a compact cardinal, Annals of Pure and Applied Logic 47 1990, 41–97.
S. Shelah, Classification of non elementary classes II. Abstract elementary classes, in Classification Theory (Chicago, IL, 1985), Lecture Notes in Mathematics, Vol. 1292, Springer, Berlin, 1987, pp. 419–497.
S. Shelah, Universal classes, in Classification Theory (Chicago, IL, 1985), Lecture Notes in Mathematics, Vol. 1292, Springer, Berlin, 1987, pp. 264–418.
S. Shelah, Categoricity for abstract classes with amalgamation, Annals of Pure and Applied Logic 98 1999, 261–294.
S. Shelah, Classification Theory for Abstract Elementary Classes, Studies in Logic (London), Vol. 18, College Publications, London, 2009.
S. Shelah, Classification Theory for Abstract Elementary Classes. Vol. 2, Studies in Logic (London), Vol. 20, College Publications, London, 2009.
S. Shelah, When first order T has limit models, Colloquium mathematicum 126 2012, 187–204.
M. VanDieren, Superstability and symmetry, Annals of Pure and Applied Logic 167 2016, 1171–1183.
M. VanDieren, Symmetry and the union of saturated models in superstable abstract elementary classes, Annals of Pure and Applied Logic 167 2016, 395–407.
S. Vasey, The categoricity spectrum of large abstract elementary classes, Selecta Mathematica 25 (2019), Article no. 65.
S. Vasey, Building independence relations in abstract elementary classes, Annals of Pure and Applied Logic 167 2016, 1029–1092.
S. Vasey, Infinitary stability theory, Archive for Mathematical Logic 55 2016, 567–592.
S. Vasey, Downward categoricity from a successor inside a good frame, Annals of Pure and Applied Logic 168 2017, 651–692.
S. Vasey, On the uniqueness property of forking in abstract elementary classes, Mathematical Logic Quarterly 63 2017, 598–604.
S. Vasey, Saturation and solvability in abstract elementary classes with amalgamation, Archive for Mathematical Logic 56 2017, 671–690.
S. Vasey, Shelah’s eventual categoricity conjecture in universal classes: part I, Annals of Pure and Applied Logic 168 2017, 1609–1642.
S. Vasey, Shelah’s eventual categoricity conjecture in universal classes: part II, Selecta Mathematica 23 2017, 1469–1506.
M. VanDieren and S. Vasey, Symmetry in abstract elementary classes with amalgamation, Archive for Mathematical Logic 56 2017, 423–452.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Vasey, S. Tameness from two successive good frames. Isr. J. Math. 235, 465–500 (2020). https://doi.org/10.1007/s11856-020-1965-4
Received:
Revised:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11856-020-1965-4