# Ballistic random walks in random environment as rough paths: convergence and area anomaly

## TL;DR

This paper proves an annealed functional CLT for ballistic random walks in random environments within the rough path topology, revealing a deterministic area anomaly linked to stochastic areas on regeneration intervals.

## Contribution

It extends rough path convergence results to a broad class of discrete processes with regeneration structures, identifying the area anomaly explicitly.

## Key findings

- Convergence in the rough path topology for ballistic random walks in random environments.
- Identification of a deterministic linear correction ('area anomaly') in the second level iterated integral.
- Convergence holds in the $rac{1}{2}$-H"older rough path topology when all moments are finite.

## Abstract

Annealed functional CLT in the rough path topology is proved for the standard class of ballistic random walks in random environment. Moreover, the `area anomaly', i.e. a deterministic linear correction for the second level iterated integral of the rescaled path, is identified in terms of a stochastic area on a regeneration interval. The main theorem is formulated in more general settings, namely for any discrete process with uniformly bounded increments which admits a regeneration structure where the regeneration times have finite moments. Here the largest finite moment translates into the degree of regularity of the rough path topology. In particular, the convergence holds in the $\alpha$-H\"older rough path topology for all $\alpha<1/2$ whenever all moments are finite, which is the case for the class of ballistic random walks in random environment. The latter may be compared to a special class of random walks in Dirichlet environments for which the regularity $\alpha<1/2$ is bounded away from $1/2$, explicitly in terms of the corresponding trap parameter.