We consider a new semidefinite programming (SDP) relaxation of the symmetric traveling salesman problem (TSP), obtained via an SDP relaxation of the more general quadratic assignment problem (QAP). We show that the new relaxation dominates the one in the paper: [D. Cvetkovic, M. Cangalovic and V. Kovacevic-Vucic. Semidefinite Programming Methods for the Symmetric Traveling Salesman Problem. In Proceedings of the 7th International IPCO Conference on Integer Programming and Combinatorial Optimization, 1999, 126--136, Springer-Verlag, London, UK.] Unlike the relaxation of Cvetkovic et al., the new SDP relaxation is not dominated by the linear programming relaxation with sub-tour elimination constraints.
SIAM Journal on Optimization, 19(4), 1559-1573, 2008. Note: Figure 5.1 is a corrected version of the incorrect figure that appeared in print.