We prove a categoricity transfer theorem for tame abstract elementary
classes.
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Theorem.
Suppose that 𝔎 is a χ-tame abstract
elementary class and satisfies the amalgamation and joint embedding
properties and has arbitrarily large models. Let
λ≥Max{χ,LS(𝔎)⁺}. If
𝔎 is categorical in
λ and λ⁺, then 𝔎 is categorical in
λ++.
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Combining this theorem with some results from [37], we derive a
form of Shelah’s Categoricity Conjecture for tame abstract elementary
classes:
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Corollary.
Suppose 𝔎 is a χ-tame abstract elementary class satisfying the
amalgamation and joint embedding properties.
Let
μ₀:= Hanf(𝔎). If χ≤ℶ(2μ₀)⁺ and
𝔎 is categorical in some
λ⁺>ℶ(2μ₀)⁺, then 𝔎 is categorical in μ for
all
μ>ℶ(2μ₀)⁺.