We prove that a (globally) subanalytic function f : X subset of Q(p)(n) -> Q(p) which is locally Lipschitz continuous with some constant C is piecewise (globally on each piece) Lipschitz continuous with possibly so...
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We prove that a (globally) subanalytic function f : X subset of Q(p)(n) -> Q(p) which is locally Lipschitz continuous with some constant C is piecewise (globally on each piece) Lipschitz continuous with possibly some other constant, where the pieces can be taken to be subanalytic. We also prove the analogous result for a subanalytic family of functions f(y) : X(y) subset of Q(p)(n) -> Q(p) depending on p-adicparameters. The statements also hold in a semi-algebraic set-up and also in a finite field extension of Q(p). These results are p-adic analogues of results of K. Kurdyka over the real numbers. To encompass the total disconnectedness of p-adic fields, we need to introduce new methods adapted to the p-adic situation.
It is known that a p-adic, locally Lipschitz continuous semi-algebraic function, is piecewise Lipschitz continuous, where finitely many pieces suffice and the pieces can be taken semi-algebraic. We prove that if the f...
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It is known that a p-adic, locally Lipschitz continuous semi-algebraic function, is piecewise Lipschitz continuous, where finitely many pieces suffice and the pieces can be taken semi-algebraic. We prove that if the function has locally Lipschitz constant 1, then it is also piecewise Lipschitz continuous with the same Lipschitz constant 1 (again, with finitely many pieces). We do this by proving the following fine preparation results for p-adic semi-algebraic functions in one variable. Any such function can be well approximated by a monomial with fractional exponent such that moreover the derivative of the monomial is an approximation of the derivative of the function. We also prove these results in parameterized versions and in the subanalytic setting.
A direct application of Zorn's Lemma gives that every Lipschitz map f : X subset of Q(p)(n) -> Q(p)(l) has an extension to a Lipschitz map (f) over tilde : Q(p)(n) -> Q(p)(l). This is analogous, but more eas...
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A direct application of Zorn's Lemma gives that every Lipschitz map f : X subset of Q(p)(n) -> Q(p)(l) has an extension to a Lipschitz map (f) over tilde : Q(p)(n) -> Q(p)(l). This is analogous, but more easy, to Kirszbraun's Theorem about the existence of Lipschitz extensions of Lipschitz maps S subset of R-n -> R-l. Recently, Fischer and Aschenbrenner obtained a definable version of Kirszbraun's Theorem. In the present paper, we prove in the p-adic context that (f) over tilde can be taken definable when f is definable, where definable means semi-algebraic or subanalytic (or, some intermediary notion). We proceed by proving the existence of definable, Lipschitz retractions of Q(p)(n) to the topological closure of X when X is definable.
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