No Small Linear Program Approximates Vertex Cover within a Factor 2 -- e

@article{Bazzi2015NoSL,
  title={No Small Linear Program Approximates Vertex Cover within a Factor 2 -- e},
  author={Ahmad Bazzi and Samuel Fiorini and Sebastian Pokutta and Ola Svensson},
  journal={2015 IEEE 56th Annual Symposium on Foundations of Computer Science},
  year={2015},
  pages={1123-1142}
}
The vertex cover problem is one of the most important and intensively studied combinatorial optimization problems. Khot and Regev [30], [31] proved that the problem is NP-hard to approximate within a factor 2 - ε, assuming the Unique Games Conjecture (UGC). This is tight because the problem has an easy 2-approximation algorithm. Without resorting to the UGC, the best in approximability result for the problem is due to Dinur and Safra [16], [17]: vertex cover is NP-hard to approximate within a… 

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