Stationary fluctuation for the occupation time of the multi-species stirring process
Xiaofeng Xue
TL;DR
The paper proves a fluctuation theorem for the occupation time of a multi-species stirring process on the lattice starting from a stationary distribution. Using a resolvent strategy and a graphical coupling with an auxiliary process, it decomposes the occupation-time fluctuations into a martingale part and a remainder, then analyzes the limit in each dimension. The main result is a dimension-dependent Gaussian limit: for $d\ge 3$ and $d=2$ the limit is a Gaussian process formed by applying $\mathcal{A}^{1/2}$ to independent Brownian motions, while for $d=1$ the limit involves a fractional Brownian motion with Hurst parameter $3/4$; in all cases, different brands interact via negative correlations, and for $d\ge 2$ the limit is independent of $k$, with a special dependence in one dimension. The graphical representation and exchanging-path construction are central to controlling correlations and proving tightness across the three regime cases.
Abstract
In this paper, we prove a fluctuation theorem for the occupation time of the multi-species stirring process on a lattice starting from a stationary distribution. Our result shows that the occupation times of different species interact with each other at the level of equilibrium fluctuation. The proof of our result utilizes the resolvent strategy introduced in \cite{Kipnis1987}. A coupling relationship between the multi-species stirring process and an auxiliary process and a graphical representation of the auxiliary process play the key roles in the proof.
