# nLab Artinian bimodule

Contents

### Context

#### Algebra

higher algebra

universal algebra

# Contents

## Idea

An Artinian bimodule is a bimodule which satisfies the descending chain condition on its subbimodules.

## Definition

Given rings $R$ and $S$ and an $R$-$S$-bimodule $B$, let $\mathrm{Mono}(B)$ be the category whose objects are $R$-$S$-subbimodules of $B$ and whose morphisms are $R$-$S$-bimodule monomorphisms. A descending chain of $R$-$S$-subbimodules is an inverse sequence of $R$-$S$-subbimodules in $\mathrm{Mono}(B)$, a sequence of $R$-$S$-subbimodules $A:\mathbb{N} \to \mathrm{Mono}(B)$ with the following dependent sequence of $R$-$S$-bimodule monomorphisms: for natural number $n \in \mathbb{N}$, a dependent $R$-$S$-bimodule monomorphism $i_n:A_{n+1} \hookrightarrow A_{n}$.

An $R$-$S$-bimodule $B$ is Artinian if it satisfies the descending chain condition on its subbimodules: for every descending chain of $R$-$S$-subbimodules $(A, i_n)$ of $B$, there exists a natural number $m \in \mathbb{N}$ such that for all natural numbers $n \geq m$, the $R$-$S$-bimodule monomorphism $i_n:A_{n+1} \hookrightarrow A_{n}$ is an $R$-$S$-bimodule isomorphism.

## Examples

A ring $R$ is Artinian if it is Artinian as a $R$-$R$-bimodule with respect to its canonical bimodule structure, with its left action $\alpha_L:R \times R \to R$ and right action $\alpha_R:R \times R \to R$ defined as its multiplicative binary operation and its biaction $\alpha:R \times R \times R \to R$ defined as its ternary product:

$\alpha_L(a, b) \coloneqq a \cdot b$
$\alpha_R(a, b) \coloneqq a \cdot b$
$\alpha(a, b, c) \coloneqq a \cdot b \cdot c$