Mathematics Colloquium : Roughness of geodesics in Liouville quantum gravity

Abstract: The metric associated with the Liouville quantum gravity (LQG) surface has been constructed through a series of recent works and several properties of its associated geodesics have been studied. In this talk we will discuss the proof of a folklore conjecture that the Euclidean Hausdorff dimension of LQG geodesics is strictly greater than 1 for all values of the so-called Liouville first passage percolation (LFPP) parameter \xi. We deduce this from a general criterion due to Aizenman and Burchard which in this case amounts to near-geometric bounds on the probabilities of certain crossing events for LQG geodesics in the number of crossings. We obtain such bounds using the axiomatic characterization of the LQG metric after obtaining a special regularity property for the Gaussian free field (GFF). If time permits, we will also discuss an analogous result for the LFPP geodesics.