首页/论文/2011.07352

arXiv 2011.073522020-11math.LO

Between reduced powers and ultrapowers, II

Ilijas Farah, Saharon Shelah

备注：: 31 pages. Minor changes, gory details added to the proof of Lemma 2.1. To appear in TAMS
发表信息：: Trans. Amer. Math. Soc. 375 No. 12 (2022) 9007--9034

英文摘要：

We prove that, consistently with ZFC, no ultraproduct of countably infinite (or separable metric, non-compact) structures is isomorphic to a reduced product of countable (or separable metric) structures associated to the Fréchet filter. Since such structures are countably saturated, the Continuum Hypothesis implies that they are isomorphic when elementarily equivalent.

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