83,763 research outputs found
Cell decomposition and classification of definable sets in p-optimal fields
We prove that for p-optimal fields (a very large subclass of p-minimal fields containing all the known examples) a cell decomposition theorem follows from methods going back to Denef’s paper [7]. We derive from it the existence of definable Skolem functions and strong p-minimality. Then we turn to strongly p-minimal fields satisfying the Extreme Value Property—a property which in particular holds in fields which are elementarily equivalent to a p-adic one. For such fields K, we prove that every definable subset of K × K d whose fibers over K are inverse images by the valuation of subsets of the value group is semialgebraic. Combining the two we get a preparation theorem for definable functions on p-optimal fields satisfying the Extreme Value Property, from which it follows that infinite sets definable over such fields are in definable bijection iff they have the same dimension
Cell Decomposition for semibounded p-adic sets
We study a reduct L\ast of the ring language where multiplication is
restricted to a neighbourhood of zero. The language is chosen such that for
p-adically closed fields K, the L\ast-definable subsets of K coincide with the
semi-algebraic subsets of K. Hence structures (K,L\ast) can be seen as the
p-adic counterpart of the o-minimal structure of semibounded sets. We show that
in this language, p-adically closed fields admit cell decomposition, using
cells similar to p-adic semi-algebraic cells. From this we can derive
quantifier-elimination, and give a characterization of definable functions. In
particular, we conclude that multi- plication can only be defined on bounded
sets, and we consider the existence of definable Skolem functions.Comment: 20 page
An example of a -minimal structure without definable Skolem functions
We show there are intermediate -minimal structures between the
semi-algebraic and sub-analytic languages which do not have definable Skolem
functions. As a consequence, by a result of Mourgues, this shows there are
-minimal structures which do not admit classical cell decomposition.Comment: 9 pages, (added missing grant acknowledgement
Integration and Cell Decomposition in -minimal Structures
We show that the class of -constructible functions is closed
under integration for any -minimal expansion of a -adic field
. This generalizes results previously known for semi-algebraic
and sub-analytic structures. As part of the proof, we obtain a weak version of
cell decomposition and function preparation for -minimal structures, a
result which is independent of the existence of Skolem functions. %The result
is obtained from weak versions of cell decomposition and function preparation
which we prove for general -minimal structures. A direct corollary is that
Denef's results on the rationality of Poincar\'e series hold in any -minimal
expansion of a -adic field .Comment: 22 page
Generic derivations on o-minimal structures
Let be a complete, model complete o-minimal theory extending the theory
RCF of real closed ordered fields in some appropriate language . We study
derivations on models . We introduce the notion
of a -derivation: a derivation which is compatible with the
-definable -functions on . We show
that the theory of -models with a -derivation has a model completion
. The derivation in models
behaves "generically," it is wildly discontinuous and its kernel is a dense
elementary -substructure of . If RCF, then
is the theory of closed ordered differential fields (CODF) as introduced by
Michael Singer. We are able to recover many of the known facts about CODF in
our setting. Among other things, we show that has as its open
core, that is distal, and that eliminates
imaginaries. We also show that the theory of -models with finitely many
commuting -derivations has a model completion.Comment: 29 page
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