A virtual five element basis for the uncountable linear orders
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866908605649780736 |
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| author | Krueger, John Moore, Justin Tatch |
| author_facet | Krueger, John Moore, Justin Tatch |
| contents | We prove that for every Aronzsajn line A and every Countryman line C, there is a proper forcing extension in which A contains an isomorphic copy of either C or its converse C*. As a corollary, we obtain answers to several related questions asked by the second author in the literature: if there is an inaccessible cardinal, then there is a proper forcing extension in which the uncountable linear orders have a five element basis; BPFA implies the existence of a five element basis for the uncountable linear orders; BPFA is equiconsistent with the conjunction of BPFA and Aronszajn tree saturation. These results are derived from new preservation results concerning subtrees of Aronszajn trees, proper forcings, and countable support iterations, generalizing work of Miyamoto, Abraham, and Shelah. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2510_03581 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | A virtual five element basis for the uncountable linear orders Krueger, John Moore, Justin Tatch Logic 03E35, 03E55, 03E57 We prove that for every Aronzsajn line A and every Countryman line C, there is a proper forcing extension in which A contains an isomorphic copy of either C or its converse C*. As a corollary, we obtain answers to several related questions asked by the second author in the literature: if there is an inaccessible cardinal, then there is a proper forcing extension in which the uncountable linear orders have a five element basis; BPFA implies the existence of a five element basis for the uncountable linear orders; BPFA is equiconsistent with the conjunction of BPFA and Aronszajn tree saturation. These results are derived from new preservation results concerning subtrees of Aronszajn trees, proper forcings, and countable support iterations, generalizing work of Miyamoto, Abraham, and Shelah. |
| title | A virtual five element basis for the uncountable linear orders |
| topic | Logic 03E35, 03E55, 03E57 |
| url | https://arxiv.org/abs/2510.03581 |