Ax-Kochen-Ershov principles for finitely ramified henselian fields
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arXiv
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| Format: | Preprint |
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2023
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| _version_ | 1866915819046305792 |
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| author | Anscombe, Sylvy Dittmann, Philip Jahnke, Franziska |
| author_facet | Anscombe, Sylvy Dittmann, Philip Jahnke, Franziska |
| contents | We study the model theory of finitely ramified henselian valued fields of fixed initial ramification, obtaining versions of the Ax-Kochen-Ershov principle as follows. We identify the induced structure on the residue field and show that once the residue field is endowed with this structure, the theory of the valued field is determined by the theories of the enriched residue field and the value group. Similarly, we show that the existential theory of the valued field is determined by the positive existential theory of the enriched residue field. We also prove that an embedding of finitely ramified henselian valued fields is existentially closed as soon as the induced embeddings of value group and residue field are existentially closed. This last result requires no enrichment of the residue field, in analogy to the corresponding result for model completeness, which holds by results of Ershov and Ziegler. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2305_12145 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Ax-Kochen-Ershov principles for finitely ramified henselian fields Anscombe, Sylvy Dittmann, Philip Jahnke, Franziska Logic 03C60, 12L12 We study the model theory of finitely ramified henselian valued fields of fixed initial ramification, obtaining versions of the Ax-Kochen-Ershov principle as follows. We identify the induced structure on the residue field and show that once the residue field is endowed with this structure, the theory of the valued field is determined by the theories of the enriched residue field and the value group. Similarly, we show that the existential theory of the valued field is determined by the positive existential theory of the enriched residue field. We also prove that an embedding of finitely ramified henselian valued fields is existentially closed as soon as the induced embeddings of value group and residue field are existentially closed. This last result requires no enrichment of the residue field, in analogy to the corresponding result for model completeness, which holds by results of Ershov and Ziegler. |
| title | Ax-Kochen-Ershov principles for finitely ramified henselian fields |
| topic | Logic 03C60, 12L12 |
| url | https://arxiv.org/abs/2305.12145 |