If $R$ is a ring and $M$ is a left $R$-module, we say that $M$ is Noetherian whenever it satisfies any of the equivalent conditions:
1N. Every ascending (under subspace inclusion) chain of submodules of $M$ stabilises,
2N. Every non-empty collection of submodules of $M$ has a maximal element under subspace inclusion,
3N. Every submodule of $M$ is finitely generated.
Whilst we say that $M$ is Artinian whenever it satisfies either of the equivalent conditions:
1A. Every descending (under subspace inclusion) chain of submodules of $M$ stabilises,
2A. Every non-empty collection of submodules of $M$ has a minimal element under subspace inclusion.
It seems to be that conditions 1N and 1A are dual, whilst conditions 2N and 2A are also dual. However I can't seem to think of a property of Artinian modules that seems obviously dual to condition 3N.
My question is whether or not there does exist such a condition?
Best Answer
Yes. 3A should be
Finite cogeneration is easy to understand if you first rephrase finite generation this way:
Then