A note on the structure theory of groups acting on the Bruhat Tits tree associated to $\mathrm{PGL}_{2}(F)$

Abstract: In this note we prove the classical decomposition theorems for certain subgroups of the automorphism group of the Bruhat-Tits tree associated to $\mathrm{PGL}_{2}(F)$, where $F$ is a local field. The results can be used to understand the representation theory of these subgroups. Moreover, we can also use the results to obtain similar decompositions for \textit{any} closed transitive subgroup of the automorphism group of \textit{any} Bruhat-Tits tree.