Planar k-Path in Subexponential Time and Polynomial Space

In the k-path problem we are given an n-vertex graph g together with an integer k and asked whether g contains a path of length k as a subgraph. We give the first subexponential time, polynomial space parameterized algorithm for k-path on planar graphs, and more generally, on h-minor-free graphs. The running time of our algorithm is o(2^{o(\sqrt{k}\log^2 k)}n^{o(1)})o(2^{o(\sqrt{k}\log^2 k)}n^{o(1)})