A characterization of Linearizable instances of the Quadratic Traveling Salesman Problem

We consider the linearization problem associated with the quadratic traveling salesman problem (QTSP). Necessary and sufficient conditions are given for a cost matrix $Q$ of QTSP to be linearizable. It is shown that these conditions can be verified in $O(n^5)$ time. Some simpler sufficient conditions for linearization are also given along with related open problems.