Logarithmic Tree Factorials

TL;DR

This paper introduces logarithmic factorials for rooted trees, linking their growth to random walk transience, harmonic measures, and branching numbers, thus generalizing factorial concepts in a combinatorial and probabilistic framework.

Contribution

It generalizes Bhargava's factorials to trees, relates factorial growth to random walk properties, and characterizes tree branching numbers using factorial sequences.

Findings

Growth of factorials relates to random walk transience.

Established an equidistribution theorem for local field subsets.

Provided a factorial-based characterization of infinite tree branching numbers.

Abstract

To any rooted tree, we associate a sequence of numbers that we call the logarithmic factorials of the tree. This provides a generalization of Bhargava's factorials to a natural combinatorial setting suitable for studying questions around generalized factorials. We discuss several basic aspects of the framework in this paper. In particular, we relate the growth of the sequence of logarithmic factorials associated to a tree to the transience of the random walk and the existence of a harmonic measure on the tree, obtain an equidistribution theorem for factorial-determining-sequences of subsets of local fields, and provide a factorial-based characterization of the branching number of infinite trees. Our treatment is based on a local weighting process in the tree which gives an effective way of constructing the factorial sequence.