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Preprint Number 1747

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1747. Will Johnson
Dp-finite fields IV: the rank 2 picture

Submission date: 20 March 2020


We investigate fields of characteristic 0 and dp-rank 2. While we do not obtain a classification, we prove that any unstable field of characteristic 0 and dp-rank 2 admits a unique definable V-topology. If this statement could be generalized to higher ranks, we would obtain the expected classification of fields of finite dp-rank.
We obtain the unique definable V-topology by investigating the “canonical topology” defined in earlier work. Contrary to earlier expectations, the canonical topology need not be a V-topology. However, we are able to characterize the canonical topology (on fields of dp-rank 2 and characteristic 0) in terms of differential valued fields.
This differential valued structure is obtained through a partial classification of “2-inflators”, a sort of generalized valuation that arises naturally in fields of finite rank.
Additionally, we give an example of a dp-rank 2 expansion of ACVF with a definable set of full rank and empty interior. This example interferes with certain strategies for proving the henselianity conjecture.

Mathematics Subject Classification: 03C45

Keywords and phrases:

Full text arXiv 2003.09130: pdf, ps.

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