Ergodic Sequence - Definition

Definition

Let be an infinite, strictly increasing sequence of positive integers. Then, given an integer q, this sequence is said to be ergodic mod q if, for all integers, one has

where

and card is the count (the number of elements) of a set, so that is the number of elements in the sequence A that are less than or equal to t, and

so is the number of elements in the sequence A, less than t, that are equivalent to k modulo q. That is, a sequence is an ergodic sequence if it becomes uniformly distributed mod q as the sequence is taken to infinity.

An equivalent definition is that the sum

\lim_{t\to\infty} \frac{1}{N(A,t)} \sum_{j; a_j\leq t}
\exp \frac{2\pi ika_j}{q} = 0

vanish for every integer k with .

If a sequence is ergodic for all q, then it is sometimes said to be ergodic for periodic systems.

Read more about this topic:  Ergodic Sequence

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