Monotone expansion
  This work, following the outline set in [B2], presents an explicit construction of a family of monotone expanders. The family is essentially defined by the Mobius action of SL_2(R) on the real line. For the proof, we show a product-growth theorem for SL_2(R). 
Jean Bourgain and Amir Yehudayoff
math.CO math.GR