Definition:Ring of Cauchy Sequences

Definition
Let $\struct {R, +, \circ, \norm {\, \cdot \,} }$ be a normed division ring.

Let $\struct {R^{\N}, +', \circ'}$ be the ring of sequences over $R$.

Let $\mathcal {C}$ be the set of Cauchy sequences on $R$.

The ring of Cauchy sequences over $R$ is the subring $\struct {\mathcal {C}, +', \circ'}$ of $R^{\N}$ with unity.

The ring operations on the ring of Cauchy sequences over $R$ are defined:
 * $\forall \sequence {x_n}, \sequence {y_n} \in R^{\N}: \sequence {x_n} +' \sequence {y_n} = \sequence {x_n + y_n}$
 * $\forall \sequence {x_n}, \sequence {y_n} \in R^{\N}: \sequence {x_n} \circ' \sequence {y_n} = \sequence {x_n \circ y_n}$

The zero of the ring of Cauchy sequences is the sequence $\tuple{0,0,0,\dots}$, where $0$ is the zero in $R$.

The unity of the ring of Cauchy sequences is the sequence $\tuple{1,1,1,\dots}$, where $1$ is the unity in $R$.

By Corollary to Cauchy Sequences form Ring with Unity, if $R$ is a valued field then the ring of Cauchy sequences over $R$ is a commutative ring with unity.

Also denoted as
It is usual to use the same symbols for the induced operations on the ring of Cauchy sequences over $R$ as for the operations that induce them.

Also see

 * Cauchy Sequences form Ring with Unity
 * Corollary to Cauchy Sequences form Ring with Unity