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Non-discrete Euclidean buildings for the Ree and Suzuki groups
- American Journal of Mathematics
- Johns Hopkins University Press
- Volume 132, Number 4, August 2010
- pp. 1113-1152
- 10.1353/ajm.0.0133
- Article
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We call a non-discrete Euclidean building a {\it Bruhat-Tits space} if
its automorphism group contains a subgroup that induces the subgroup
generated by all the root groups of a root datum of the building at
infinity. This is the class of non-discrete Euclidean buildings
introduced and studied by Bruhat and Tits. We give the complete
classification of Bruhat-Tits spaces whose building at infinity is the
fixed point set of a polarity of an ambient building of type $\hbox{\sf
B}_2$, $\hbox{\sf F}_4$ or $\hbox{\sf G}_2$ associated with a Ree or Suzuki
group endowed with the usual root datum. (In the $\hbox{\sf B}_2$ and
$\hbox{\sf G}_2$ cases, this fixed point set is a building of rank one; in
the $\hbox{\sf F}_4$ case, it is a generalized octagon whose Weyl group is
not crystallographic.) We also show that each of these Bruhat-Tits
spaces has a natural embedding in the unique Bruhat-Tits space whose
building at infinity is the corresponding ambient building.