The model theory of tame valued fields Preliminary version

A henselian valued field K is called a tame field if its separable-algebraic closure Ksep is a tame extension, that is, Ksep is equal to the ramification field of the normal extension Ksep|K. Every algebraically maximal Kaplansky field is a tame field, but not conversely. We prove Ax–Kochen–Ershov Principles for tame fields. This leads to model completeness and completeness results relative to value group and residue field. As the maximal immediate extensions of tame fields will in general not be unique, the proofs have to use much deeper valuation theoretical results than those for other classes of valued fields which have already been shown to satisfy Ax–Kochen–Ershov Principles. The results of this paper have been applied to gain insight in the Zariski space of places of an algebraic function field, and in the model theory of large fields. This is a preliminary version, with several proofs (in particular, the model theoretic nonsense) omitted. Apologies for any inconvenience due to lack of coherence in some places and for missing references.