Weak amenability of Lie groups made discrete
  We completely characterize connected Lie groups all of whose countable subgroups are weakly amenable. We also provide a characterization of connected semisimple Lie groups that are weakly amenable. Finally, we show that a connected Lie group is weakly amenable if the group is weakly amenable as a discrete group. 
S{\o}ren Knudby
math.FA math.GR math.OA