Abstract
We prove that the Katětov order on Borel ideals (1) contains a copy of \(\mathcal {P}(\omega )/\mathbf {Fin}\), consequently it has increasing and decreasing chains of lenght 𝔟; (2) the sequence F i n α (α < ω 1) is a strictly increasing chain; and (3) in the Cohen model, Katětov order does not contain any increasing nor decreasing chain of length 𝔠, answering a question of Hrušák (2011).
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Second author was supported by grants UMSNH-CIC-9.30 and CONACYT-CB-169078
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Guzmán-González, O., Meza-Alcántara, D. Some Structural Aspects of the Katětov Order on Borel Ideals. Order 33, 189–194 (2016). https://doi.org/10.1007/s11083-015-9358-8
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DOI: https://doi.org/10.1007/s11083-015-9358-8