scholarly journals THE MODEL COMPANION OF DIFFERENTIAL FIELDS WITH FREE OPERATORS

2016 ◽  
Vol 81 (2) ◽  
pp. 493-509
Author(s):  
OMAR LEÓN SÁNCHEZ ◽  
RAHIM MOOSA
Keyword(s):  
Mathematical Logic ◽  
Characteristic Zero ◽  
Differential Algebra ◽  
Model Companion ◽  
Finite Algebras ◽  
Closed Fields ◽  
Hensel’S Lemma ◽  
Differential Fields ◽  
Theory Of Fields ◽  
Model Theory Of Fields

AbstractA model companion is shown to exist for the theory of partial differential fields of characteristic zero equipped with free operators that commute with the derivations. The free operators here are those introduced in [R. Moosa and T. Scanlon, Model theory of fields with free operators in characteristic zero, Journal of Mathematical Logic 14(2), 2014]. The proof relies on a new lifting lemma in differential algebra: a differential version of Hensel’s Lemma for local finite algebras over differentially closed fields.

scholarly journals Model theory of fields with free operators in characteristic zero

2014 ◽  
Vol 14 (02) ◽  
pp. 1450009 ◽  
Author(s):  
Rahim Moosa ◽  
Thomas Scanlon
Keyword(s):  
Free Algebra ◽  
Model Theory ◽  
Characteristic Zero ◽  
Model Companion ◽  
Finite Dimensional ◽  
Differential Fields ◽  
Theory Of Fields ◽  
Model Theory Of Fields

Generalizing and unifying the known theorems for difference and differential fields, it is shown that for every finite free algebra scheme 𝒟 over a field A of characteristic zero, the theory of 𝒟-fields has a model companion 𝒟-CF0 which is simple and satisfies the Zilber dichotomy for finite-dimensional minimal types.

Some model theory for almost real closed fields

1996 ◽  
Vol 61 (4) ◽  
pp. 1121-1152 ◽  
Author(s):  
Françoise Delon ◽  
Rafel Farré
Keyword(s):  
Model Theory ◽  
Residue Field ◽  
Elementary Equivalence ◽  
First Order ◽  
Valuation Rings ◽  
Closed Fields ◽  
Theory Of Fields ◽  
Model Theory Of Fields ◽  
Elementary Inclusion ◽  
Henselian Valuation

AbstractWe study the model theory of fields k carrying a henselian valuation with real closed residue field. We give a criteria for elementary equivalence and elementary inclusion of such fields involving the value group of a not necessarily definable valuation. This allows us to translate theories of such fields to theories of ordered abelian groups, and we study the properties of this translation. We also characterize the first-order definable convex subgroups of a given ordered abelian group and prove that the definable real valuation rings of k are in correspondence with the definable convex subgroups of the value group of a certain real valuation of k.

Differentially algebraic group chunks

1990 ◽  
Vol 55 (3) ◽  
pp. 1138-1142 ◽  
Author(s):  
Anand Pillay
Keyword(s):  
Algebraic Group ◽  
Characteristic Zero ◽  
Quantifier Elimination ◽  
Closed Field ◽  
Zariski Topology ◽  
First Order ◽  
Differential Field ◽  
Closed Fields ◽  
Differential Fields ◽  
Algebraically Closed Fields

We point out that a group first order definable in a differentially closed field K of characteristic 0 can be definably equipped with the structure of a differentially algebraic group over K. This is a translation into the framework of differentially closed fields of what is known for groups definable in algebraically closed fields (Weil's theorem).I restrict myself here to showing (Theorem 20) how one can find a large “differentially algebraic group chunk” inside a group defined in a differentially closed field. The rest of the translation (Theorem 21) follows routinely, as in [B].What is, perhaps, of interest is that the proof proceeds at a completely general (soft) model theoretic level, once Facts 1–4 below are known.Fact 1. The theory of differentially closed fields of characteristic 0 is complete and has quantifier elimination in the language of differential fields (+, ·,0,1, −1,d).Fact 2. Affine n-space over a differentially closed field is a Noetherian space when equipped with the differential Zariski topology.Fact 3. If K is a differentially closed field, k ⊆ K a differential field, and a and are in k, then a is in the definable closure of k ◡ iff a ∈ ‹› (where k ‹› denotes the differential field generated by k and).Fact 4. The theory of differentially closed fields of characteristic zero is totally transcendental (in particular, stable).

Notes on the stability of separably closed fields

1979 ◽  
Vol 44 (3) ◽  
pp. 412-416 ◽  
Author(s):  
Carol Wood
Keyword(s):  
Differential Algebra ◽  
Complete Theory ◽  
Model Completeness ◽  
Closed Fields ◽  
Superstable Theories ◽  
Basic Facts ◽  
The Stability ◽  
Differential Fields

AbstractThe stability of each of the theories of separably closed fields is proved, in the manner of Shelah's proof of the corresponding result for differentially closed fields. These are at present the only known stable but not superstable theories of fields. We indicate in §3 how each of the theories of separably closed fields can be associated with a model complete theory in the language of differential algebra. We assume familiarity with some basic facts about model completeness [4], stability [7], separably closed fields [2] or [3], and (for §3 only) differential fields [8].

scholarly journals FIELDS WITH SEVERAL COMMUTING DERIVATIONS

2014 ◽  
Vol 79 (01) ◽  
pp. 1-19 ◽  
Author(s):  
DAVID PIERCE
Keyword(s):  
Natural Number ◽  
Geometric Characterization ◽  
Model Companion ◽  
First Order ◽  
Existentially Closed ◽  
Differential Fields ◽  
Theory Of Fields ◽  
Differential Varieties

AbstractFor every natural numberm, the existentially closed models of the theory of fields withmcommuting derivations can be given a first-order geometric characterization in several ways. In particular, the theory of these differential fields has a model-companion. The axioms are that certain differential varieties determined by certain ordinary varieties are nonempty. There is no restriction on the characteristic of the underlying field.

Differential Polynomials

2017 ◽  
Author(s):  
Matthias Aschenbrenner ◽  
Lou van den Dries ◽  
Joris van der Hoeven
Keyword(s):  
Characteristic Zero ◽  
Natural Setting ◽  
Differential Polynomials ◽  
Differential Field ◽  
Closed Fields ◽  
Basic Facts ◽  
Differential Fields

This chapter deals with differential polynomials. It first presents some basic facts about differential fields that are of characteristic zero with one distinguished derivation, along with their extensions. It then considers various decompositions of differential polynomials in their natural setting, along with valued differential fields and the property of continuity of the derivation with respect to the valuation topology. It also discusses the gaussian extension of the valuation to the ring of differential polynomials and concludes with some basic results on simple differential rings and differentially closed fields. In contrast to the corresponding notions for fields, the chapter shows that differential fields always have proper d-algebraic extensions, and the differential closure of a differential field K is not always minimal over K.

scholarly journals DEFINABLE GROUPS IN DCFA

2019 ◽  
Vol 26 (2) ◽  
pp. 179-195
Author(s):  
RONALD BUSTAMANTE MEDINA
Keyword(s):  
Algebraic Group ◽  
Characteristic Zero ◽  
Abelian Groups ◽  
Model Companion ◽  
Definable Groups ◽  
Differential Fields

E. Hrushovski proved that the theory of difference-differential fields of characteristic zero has a model-companion. We denote it DCFA. In this paper we study definable abelian groups in a model of DCFA. First we prove that such a group is embeddable on an algebraic group. Then, we study one-basedeness, stability and stable embeddability of abelian definable groups.

scholarly journals Existentially closed fields with finite group actions

2018 ◽  
Vol 18 (01) ◽  
pp. 1850003 ◽  
Author(s):  
Daniel M. Hoffmann ◽  
Piotr Kowalski
Keyword(s):  
Finite Group ◽  
Model Theory ◽  
Group Scheme ◽  
General Context ◽  
Finite Group Actions ◽  
Existentially Closed ◽  
Closed Fields ◽  
A Finite Group ◽  
Theory Of Fields ◽  
Model Theory Of Fields

We study algebraic and model-theoretic properties of existentially closed fields with an action of a fixed finite group. Such fields turn out to be pseudo-algebraically closed in a rather strong sense. We place this work in a more general context of the model theory of fields with a (finite) group scheme action.

Minimal types in separably closed field

2000 ◽  
Vol 65 (3) ◽  
pp. 1443-1450 ◽  
Author(s):  
Zoé Chatzidakis ◽  
Carol Wood
Keyword(s):  
Model Theory ◽  
Abelian Varieties ◽  
Transcendence Degree ◽  
Closed Field ◽  
Closed Fields ◽  
Theory Of Fields ◽  
Model Theory Of Fields

In [1], examples of types of U-rank 1 (i.e., minimal types) in the theories of separably closed fields were constructed, en route to displaying certain dimension phenomena. We construct here additional examples with U-rank 1 and of various transcendence degrees over arbitrary separably closed fields. Our examples include ones which are minimal but of infinite transcendence degree, i.e., not thin. Our interest in building new examples was piqued after seeing the role played by minimal types over separably closed fields in Hrushovski's analysis of abelian varieties. This article is the result of several working sessions between the authors at Wesleyan University and Paris 7, and was completed during the Model Theory of Fields program at MSRI in 1998. We are grateful for the hospitality and support of all three institutions. We thank Elisabeth Bouscaren and Françoise Delon for reading an earlier version of this paper, providing useful suggestions and corrections.

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