1. Maps on Ultrametric Spaces, Hensel's Lemma, and Differential Equations Over Valued Fields
- Author
-
Franz-Viktor Kuhlmann
- Subjects
Discrete mathematics ,Lemma (mathematics) ,Algebra and Number Theory ,Aubin–Lions lemma ,Céa's lemma ,Commutative Algebra (math.AC) ,Mathematics - Commutative Algebra ,Implicit function theorem ,Surjective function ,12J10, 12J20 ,FOS: Mathematics ,Differential algebra ,Ultrametric space ,Hensel's lemma ,Mathematics - Abstract
We give a criterion for maps on ultrametric spaces to be surjective and to preserve spherical completeness. We show how Hensel's Lemma and the multi-dimensional Hensel's Lemma follow from our result. We give an easy proof that the latter holds in every henselian field. We also prove a basic infinite-dimensional Implicit Function Theorem. Further, we apply the criterion to deduce various versions of Hensel's Lemma for polynomials in several additive operators, and to give a criterion for the existence of integration and solutions of certain differential equations on spherically complete valued differential fields, for both valued D-fields in the sense of Scanlon, and differentially valued fields in the sense of Rosenlicht. We modify the approach so that it also covers logarithmic-exponential power series fields. Finally, we give a criterion for a sum of spherically complete subgroups of a valued abelian group to be spherically complete. This in turn can be used to determine elementary properties of power series fields in positive characteristic., 47 pages
- Published
- 2011