Central limit theorems and moderate deviations for additive functionals of SSEP on regular trees

In this paper, we are concerned with the symmetric simple exclusion process (SSEP) on the regular tree $\mathcal{T}_d$. A central limit theorem and a moderate deviation principle of the additive functional of the process are proved, which include the CLT and the MDP of the occupation time as special cases. A graphical representation of the SSEP plays the key role in proofs of the main results, by which we can extend the martingale decomposition formula introduced in Kipnis (1987) for the occupation time to the case of general additive functionals.