Commensurators of some non-uniform tree lattices and Moufang twin trees

Peter Abramenko, Bertrand Remy

Sh. Mozes showed that the commensurator of the lattice ${\mathrm{PSL}}_2({\mathbf{F}}_p[t{}^{-1}])$ is dense in the full automorphism group of the Bruhat-Tits tree of valency $p+…