*Matthias Aschenbrenner, Lou van den Dries, and Joris van der Hoeven*

- Published in print:
- 2017
- Published Online:
- October 2017
- ISBN:
- 9780691175423
- eISBN:
- 9781400885411
- Item type:
- chapter

- Publisher:
- Princeton University Press
- DOI:
- 10.23943/princeton/9780691175423.003.0017
- Subject:
- Mathematics, Computational Mathematics / Optimization

This chapter considers the theory Tsuperscript nl of ω-free newtonian Liouville closed H-fields that eliminates quantifiers in a certain natural language. This theory has two completions: in the ...
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This chapter considers the theory Tsuperscript nl of ω-free newtonian Liouville closed H-fields that eliminates quantifiers in a certain natural language. This theory has two completions: in the first, the models are the models of Tsuperscript nl with small derivation; in the second, the derivation is not small. One can move from models of the first completion to models of the second completion by compositional conjugation. The chapter begins with a discussion of extensions controlled by asymptotic couples and then shows the uniqueness-up-to-isomorphism of Newton-Liouville closures of ω-free H-fields. It then constructs a ω-free ΔΩ-field extension of K with a useful semiuniversal property. It also deduces Theorem 7 about quantifier elimination with various interesting consequences and concludes by specifying the language of ΔΩ-fields and demonstrating the elimination of quantifiers with applications.Less

This chapter considers the theory *T*superscript *nl* of ω-free newtonian Liouville closed *H*-fields that eliminates quantifiers in a certain natural language. This theory has two completions: in the first, the models are the models of *T*superscript *nl* with small derivation; in the second, the derivation is not small. One can move from models of the first completion to models of the second completion by compositional conjugation. The chapter begins with a discussion of extensions controlled by asymptotic couples and then shows the uniqueness-up-to-isomorphism of Newton-Liouville closures of ω-free *H*-fields. It then constructs a ω-free ΔΩ-field extension of *K* with a useful semiuniversal property. It also deduces Theorem 7 about quantifier elimination with various interesting consequences and concludes by specifying the language of ΔΩ-fields and demonstrating the elimination of quantifiers with applications.

*Matthias Aschenbrenner, Lou van den Dries, and Joris van der Hoeven*

- Published in print:
- 2017
- Published Online:
- October 2017
- ISBN:
- 9780691175423
- eISBN:
- 9781400885411
- Item type:
- book

- Publisher:
- Princeton University Press
- DOI:
- 10.23943/princeton/9780691175423.001.0001
- Subject:
- Mathematics, Computational Mathematics / Optimization

Asymptotic differential algebra seeks to understand the solutions of differential equations and their asymptotics from an algebraic point of view. The differential field of transseries plays a ...
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Asymptotic differential algebra seeks to understand the solutions of differential equations and their asymptotics from an algebraic point of view. The differential field of transseries plays a central role in the subject. Besides powers of the variable, these series may contain exponential and logarithmic terms. Over the last thirty years, transseries emerged variously as super-exact asymptotic expansions of return maps of analytic vector fields, in connection with Tarski's problem on the field of reals with exponentiation, and in mathematical physics. Their formal nature also makes them suitable for machine computations in computer algebra systems. This book validates the intuition that the differential field of transseries is a universal domain for asymptotic differential algebra. It does so by establishing in the realm of transseries a complete elimination theory for systems of algebraic differential equations with asymptotic side conditions. Beginning with background chapters on valuations and differential algebra, the book goes on to develop the basic theory of valued differential fields, including a notion of differential-henselianity. Next, H-fields are singled out among ordered valued differential fields to provide an algebraic setting for the common properties of Hardy fields and the differential field of transseries. The study of their extensions culminates in an analogue of the algebraic closure of a field: the Newton–Liouville closure of an H-field. This paves the way to a quantifier elimination with interesting consequences.Less

Asymptotic differential algebra seeks to understand the solutions of differential equations and their asymptotics from an algebraic point of view. The differential field of transseries plays a central role in the subject. Besides powers of the variable, these series may contain exponential and logarithmic terms. Over the last thirty years, transseries emerged variously as super-exact asymptotic expansions of return maps of analytic vector fields, in connection with Tarski's problem on the field of reals with exponentiation, and in mathematical physics. Their formal nature also makes them suitable for machine computations in computer algebra systems. This book validates the intuition that the differential field of transseries is a universal domain for asymptotic differential algebra. It does so by establishing in the realm of transseries a complete elimination theory for systems of algebraic differential equations with asymptotic side conditions. Beginning with background chapters on valuations and differential algebra, the book goes on to develop the basic theory of valued differential fields, including a notion of differential-henselianity. Next, *H*-fields are singled out among ordered valued differential fields to provide an algebraic setting for the common properties of Hardy fields and the differential field of transseries. The study of their extensions culminates in an analogue of the algebraic closure of a field: the Newton–Liouville closure of an *H*-field. This paves the way to a quantifier elimination with interesting consequences.