23 research outputs found
Group-theoretic compactification of Bruhat-Tits buildings
Let GF denote the rational points of a semisimple group G over a
non-archimedean local field F, with Bruhat-Tits building X. This paper contains
five main results. We prove a convergence theorem for sequences of parahoric
subgroups of GF in the Chabauty topology, which enables to compactify the
vertices of X. We obtain a structure theorem showing that the Bruhat-Tits
buildings of the Levi factors all lie in the boundary of the compactification.
Then we obtain an identification theorem with the polyhedral compactification
(previously defined in analogy with the case of symmetric spaces). We finally
prove two parametrization theorems extending the BruhatTits dictionary between
maximal compact subgroups and vertices of X: one is about Zariski connected
amenable subgroups, and the other is about subgroups with distal adjoint
action
Finite group actions on reductive groups and buildings and tamely-ramified descent in Bruhat-Tits theory
The purpose of the paper is to give a new approach to tamely-ramified descent
in Bruhat-Tits theory. This descent was first studied by Guy Rousseau in his
thesis.Comment: 28 pages. arXiv admin note: text overlap with arXiv:1611.0743
Completed Iwahori-Hecke algebras and parahorical Hecke algebras for Kac-Moody groups over local fields
Let G be a split Kac-Moody group over a non-archimedean local field. We
define a completion of the Iwahori-Hecke algebra of G. We determine its center
and prove that it is isomorphic to the spherical Hecke algebra of G using the
Satake isomorphism. This is thus similar to the situation of reductive groups.
Our main tool is the masure I associated to this setting, which is the analogue
of the Bruhat-Tits building for reductive groups. Then, for each special and
spherical facet F, we associate a Hecke algebra. In the Kac-Moody setting, this
construction was known only for the spherical subgroup and for the Iwahori
subgroup