Title: Galois descent of semi-affinoid spaces,
Abstract: We study the Galois descent of semi-affinoid non-archimedean analytic spaces.
These are the non-archimedean analytic spaces which admit an affine special
formal scheme as model over a complete discrete valuation ring, such as for
example open or closed polydiscs or polyannuli. Using Weil restrictions and
Galois fixed loci for semi-affinoid spaces and their formal models, we describe
a formal model of a $K$-analytic space $X$, provided that $X\otimes_KL$ is
semi-affinoid for some finite tamely ramified extension $L$ of $K$. As an
application, we study the forms of analytic annuli that are trivialized by a
wide class of Galois extensions that includes totally tamely ramified
extensions. In order to do so, we first establish a Weierstrass preparation
result for analytic functions on annuli, and use it to linearize finite order
automorphisms of annuli. Finally, we explain how from these results one can
deduce a non-archimedean analytic proof of the existence of resolutions of
singularities of surfaces in characteristic zero.