
arXiv: 2202.04151
We study approximate ℵ 0 -categoricity of theories of beautiful pairs of randomizations, in the sense of continuous logic. This leads us to disprove a conjecture of Ben Yaacov, Berenstein and Henson, by exhibiting ℵ 0 -categorical, ℵ 0 -stable metric theories Q for which the corresponding theory Q P of beautiful pairs is not approximately ℵ 0 -categorical, i.e., has separable models that are not isomorphic even up to small perturbations of the smaller model of the pair. The theory Q of randomized infinite vector spaces over a finite field is such an example. On the positive side, we show that the theory of beautiful pairs of randomized infinite sets is approximately ℵ 0 -categorical. We also prove that a related stronger property, which holds in that case, is preserved under various natural constructions, and formulate our guesswork for the general case.
beautiful pairs, 03C66, 03C45, 03C35, 22F50, Continuous model theory, model theory of metric structures, Mathematics - Logic, randomization, approximate categoricity, Categoricity and completeness of theories, continuous logic, FOS: Mathematics, [MATH.MATH-LO] Mathematics [math]/Logic [math.LO], \(\aleph_0\)-stability, Classification theory, stability, and related concepts in model theory, Infinite automorphism groups, Logic (math.LO), \(\aleph_0\)-categoricity
beautiful pairs, 03C66, 03C45, 03C35, 22F50, Continuous model theory, model theory of metric structures, Mathematics - Logic, randomization, approximate categoricity, Categoricity and completeness of theories, continuous logic, FOS: Mathematics, [MATH.MATH-LO] Mathematics [math]/Logic [math.LO], \(\aleph_0\)-stability, Classification theory, stability, and related concepts in model theory, Infinite automorphism groups, Logic (math.LO), \(\aleph_0\)-categoricity
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