Diameter and spectral gap for planar graphs
arXiv:1204.4435
Abstract
We prove that the spectral gap of a finite planar graph is bounded by $λ_1(X)\le C(\frac{\log(\diam X)}{\diam X})^2$ where depends only on the degree of . We then give a sequence of such graphs showing the the above estimate cannot be improved. This yields a negative answer to a question of Benjamini and Curien on the mixing times of the simple random walk on planar graphs.
Fixed an error. Streamlined proof