Improved Approximation Lower Bounds for Vertex Cover on Power Law Graphs   and Some Generalizations
  We prove new explicit inapproximability results for the Vertex Cover Problem on the Power Law Graphs and some functional generalizations of that class of graphs. Our results depend on special bounded degree amplifier constructions for those classes of graphs and could be also of independent interest. 
Mikael Gast, Mathias Hauptmann, Marek Karpinski
cs.CC cs.DM cs.DS math.CO math.OC