Theory of Computing Article Abstract ------------------------------------ Title : Proving Integrality Gaps without Knowing the Linear Program Authors : Sanjeev Arora, B{\'e}la Bollob{\'a}s, L{\'a}szl{\'o} Lov{\'a}sz, Iannis Tourlakis Volume : 2 Number : 2 Pages : 19-51 URL : http://www.theoryofcomputing.org/articles/main/v002/a002/index.html Abstract -------- Proving integrality gaps for linear relaxations of NP optimization problems is a difficult task and usually undertaken on a case-by-case basis. We initiate a more systematic approach. We prove an integrality gap of 2-o(1) for three families of linear relaxations for vertex cover, and our methods seem relevant to other problems as well.