Over an artinian ring every nonzero module has a simple submodule?

690 Views Asked by At

I want to prove this :

Over an artinian ring every nonzero module has a simple submodule.

But the same statement for Noetherian rings is not true.

Is there any hint how to show that?

Thank you very much.

1

There are 1 best solutions below

5
On BEST ANSWER

Without loss of generality, we can assume that the module is finitely generated (just pick a finitely generated submodule).

A finitely generated module over an Artinian ring is itself Artinian. In particular, every descending chain of submodules stabilises.

So if you didn't have a simple submodule, every submodule has a proper non-trival submodule, leading to an infinite strictly descending chain. This would contradict the module being Artinian.