# Polynomially growing harmonic functions on connected groups

## TL;DR

This paper characterizes polynomial volume growth in connected groups through the finite dimensionality of harmonic functions with linear growth, revealing differences from discrete groups and extending understanding of geometric group properties.

## Contribution

It establishes a new equivalence between polynomial growth and harmonic function spaces in connected groups, filling a gap in the theory beyond nilpotent and solvable cases.

## Key findings

- Connected groups of polynomial growth have finite-dimensional linear growth harmonic functions.
- The characterization differs from the discrete case, where only solvable groups are understood.
- Examples show some connected groups of polynomial growth are not nilpotent by compact.

## Abstract

We study the connection between the dimension of certain spaces of harmonic functions on a group and its geometric and algebraic properties. Our main result shows that (for sufficiently "nice" random walk measures) a connected, compactly generated, locally compact group has polynomial volume growth if and only if the space of linear growth harmonic functions has finite dimension. This characterization is interesting in light of the fact that Gromov's theorem regarding finitely generated groups of polynomial growth does not have an analog in the connected case. That is, there are examples of connected groups of polynomial growth that are not nilpotent by compact. Also, the analogous result for the discrete case has only been established for solvable groups, and is still open for general finitely generated groups.