Given a summable sequence $a_i$ of real numbers, theorems of Levi and later Agnew characterize the permutations $\pi: \mathbb N \mapsto \mathbb N$ which are sum preserveing: that is

$$ \lim_{n\to\infty}\sum_{i=1}^n a_{i} = \lim_{n\to\infty}\sum_{i=1}^n a_{\pi(i)} $$

I would like to know of any similar research into permutations that preserve the Cesaro mean. That is, given a sequence $b_i \in \ell^\infty$, is there any characterization of permutations which $$ \lim_{n\to\infty} \frac{1}{n} \sum_{i=1}^n b_i = \lim_{n\to\infty} \frac{1}{n} \sum_{i=1}^n b_{\pi(i)}$$

anyCesaro mean ? – Pietro Majer Jan 29 '13 at 22:11