Stephan Kreutzer, Disjoint Paths in Graphs and Digraphs
One of the important algorithmic consequences of Robertson and Seymour's Graph Minor Project is their proof that the k-Vertex-Disjoint Paths problem is fixed-parameter tractable on the class of all undirected graphs, that is, solvable in time $f(k) \cdot n^c$, for some function $f$ and constant $c$. For directed graphs the problem is significantly harder: the …