A new approach to unramified descent in Bruhat-Tits theory

Abstract

The purpose of the paper is to present an alternative approach to unramified descent in Bruhat-Tits theory of reductive groups over nonarchimedean local fields. This approach appears to be conceptually simpler than the approach in the papers of Bruhat and Tits.

arXiv commentThe earlier version has been revised to improve the exposition, to add more results and more details. The conditions that the residue field is perfect and of dimension less than or equal to 1 has been removed from the earlier versions. A new section (section 4) has been added to discuss hyperspecial points and hyperspecial parahoric subgroups