Definition:Infinite Cyclic Group

Definition
An infinite cyclic group is a cyclic group $G$ such that:
 * $\forall n \in \Z_{> 0}: n > 2 \implies \not \exists a \in G, a \ne e: a^n = e$

Group Presentation
The presentation of an infinite cyclic group is:


 * $G = \gen a$

This specifies $G$ as being generated by a single element of infinite order.

From Integers under Addition form Infinite Cyclic Group, the additive group of integers $\struct {\Z, +}$ forms an infinite cyclic group.

Thus the notation $\Z$ is often used for the infinite cyclic group.

This is justified as, from Cyclic Groups of Same Order are Isomorphic, $\Z$ is isomorphic to $\gen a$.

Also known as
A cyclic group is also known as a free group on one generator.

If $G$ is an infinite cyclic group generated by $a \in G$, then $a$ is an element of infinite order, and all the powers of $a$ are different.

Thus:


 * $G = \set {\ldots, a^{-3}, a^{-2}, a^{-1}, e, a, a^2, a^3, \ldots}$

Also see

 * Cyclic Group is Infinite iff Equal Power implies Equal Indices
 * Infinite Cyclic Group is Free Group on One Generator