Definable retractions and a non-Archimedean Tietze--Urysohn theorem over Henselian valued fields

Abstract

We prove the existence of definable retractions onto arbitrary closed subsets of $K^n$ definable over Henselian valued fields $K$. Hence directly follows non-Archimedian analogues of the Tietze--Urysohn and Dugundji theorems on extending continuous definable functions. The main ingredients of the proof are a description of definable sets due to van den Dries, resolution of singularities and our closedness theorem.