Published online by Cambridge University Press: 14 July 2016
Kipnis and Varadhan (1986) showed that, for an additive functional, S n say, of a reversible Markov chain, the condition E[S n 2] / n → κ ∈ (0, ∞) implies the convergence of the conditional distribution of S n / √E[S n 2], given the starting point, to the standard normal distribution. We revisit this question under the weaker condition, E[S n 2] = n l(n), where l is a slowly varying function. It is shown by example that the conditional distributions of S n / √E[S n 2] need not converge to the standard normal distribution in this case; and sufficient conditions for convergence to a (possibly nonstandard) normal distribution are developed.