A better differential approximation ratio for symmetric TSP

In this paper, we study the approximability properties of symmetric TSP under an approximation measure called the differential ratio. More precisely, we improve up to 3/4−ε (for any ε>0) the best differential ratio of 2/3 known so far, given in Hassin and Khuller, [R. Hassin, S. Khuller, z-approximations, J. Algorithms, 41 (2) (2001) 429–442].