Trivalent expanders and hyperbolic surfaces
  We introduce a family of trivalent expanders which tessellate compact hyperbolic surfaces with large isometry groups. We compare this family with Platonic graphs and modifications of them and prove topological and spectral properties of these families. 
Ioannis Ivrissimtzis, Norbert Peyerimhoff and Alina Vdovina
math.CO