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Stable domination and independence in algebraically closed valued fields

Deirdre Haskell·Ehud Hrushovski·Dugald Macpherson
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Abstract

We seek to create tools for a model-theoretic analysis of types in algebraically closed valued fields (ACVF). We give evidence to show that a notion of 'domination by stable part' plays a key role. In Part A, we develop a general theory of stably dominated types, showing they enjoy an excellent independence theory, as well as a theory of definable types and germs of definable functions. In Part B, we show that the general theory applies to ACVF. Over a sufficiently rich base, we show that every type is stably dominated over its image in the value group. For invariant types over any base, stable domination coincides with a natural notion of `orthogonality to the value group'. We also investigate other notions of independence, and show that they all agree, and are well-behaved, for stably dominated types. One of these is used to show that every type extends to an invariant type; definable types are dense. Much of this work requires the use of imaginary elements. We also show existence of prime models over reasonable bases, possibly including imaginaries.

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Deirdre Haskell, Ehud Hrushovski, Dugald Macpherson. 2006-11-20. Stable domination and independence in algebraically closed valued fields. https://arxiv.org/abs/math/0511310

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