Distributional limits of Riemannian manifolds and graphs with sublinear genus growth

TL;DR

This paper explores the distributional limits of Riemannian manifolds with bounded curvature and applies these findings to improve understanding of random walks on planar graph limits, linking genus growth to graph properties.

Contribution

It extends the concept of distributional limits from graphs to Riemannian manifolds with quasi-conformal conditions and applies this to analyze genus growth and random walk recurrence.

Findings

Limits of Riemannian manifolds with bounded curvature are characterized.

Genus of graphs in an expander family grows at least linearly with vertices.

Improved criteria for recurrence of random walks on graph limits.

Abstract

Benjamini and Schramm introduced the notion of distributional limit of a sequence of graphs with uniformly bounded valence and studied such limits in the case that the involved graphs are planar. We investigate distributional limits of sequences of Riemannian manifolds with bounded curvature which satisfy certain condition of quasi-conformal nature. We then apply our results to somewhat improve Benjamini's and Schramm's original result on the recurrence of the simple random walk on limits of planar graphs. For instance, as an application give a proof of the fact that for graphs in an expander family, the genus of each graph is bounded from below by a linear function of the number of vertices.