Finitely generated groups and harmonic functions of slow growth

Abstract: In this paper, we are mainly concerned with $(\mathbb{G},\mu)$-harmonic functions that grow at most polynomially, where $\mathbb{G}$ is a finitely generated group with a probability measure $\mu$. In the initial part of the paper, we focus on Lipschitz harmonic functions and how they descend onto finite index subgroups. We discuss the relations between Lipschitz harmonic functions and harmonic functions of linear growth and conclude that for groups of polynomial growth, they coincide. In the latter part of the paper, we specialise to positive harmonic functions and give a characterisation for strong Liouville property in terms of the Green's function. We show that the existence of a non-constant positive harmonic function of polynomial growth guarantees that the group cannot have polynomial growth.