Noetherian Modules - Bland - Proposition 4.2.3

  • Context: MHB 
  • Thread starter Thread starter Math Amateur
  • Start date Start date
  • Tags Tags
    Modules
Click For Summary
SUMMARY

The discussion focuses on Proposition 4.2.3 from Paul E. Bland's "Rings and Their Modules," specifically the proof of the implication $$ (2) \Longrightarrow (3) $$. It establishes that if $$N^* \ne N$$ and $$x \in N - N^*$$, then $$N^* + xR$$ is a finitely generated submodule of $$N$$ that properly contains $$N^*$$. The participants confirm that since both $$N^*$$ and $$xR$$ are modules, their sum is also a module, and since $$x$$ is an element of $$N$$, it ensures that $$N^* + xR$$ is indeed a submodule of $$N$$.

PREREQUISITES
  • Understanding of Noetherian and Artinian modules
  • Familiarity with finitely generated modules
  • Knowledge of module theory, specifically submodules
  • Basic concepts of ring theory as presented in Bland's book
NEXT STEPS
  • Study the definitions and properties of Noetherian and Artinian modules in detail
  • Explore the concept of finitely generated modules and their implications
  • Review the proof techniques used in module theory, particularly in Bland's work
  • Investigate the relationship between submodules and their generating sets
USEFUL FOR

Mathematicians, graduate students, and researchers in algebra, particularly those focusing on module theory and its applications in ring theory.

Math Amateur
Gold Member
MHB
Messages
3,920
Reaction score
48
I am reading Paul E. Bland's book, "Rings and Their Modules".

I am trying to understand Chapter 4, Section 4.2 on Noetherian and Artinian modules and need help with the proof of $$ (2) \Longrightarrow (3) $$ in Proposition 4.2.3.

Proposition 4.2.3 and its proof read as follows:

View attachment 3658
View attachment 3659

In the proof of $$ (2) \Longrightarrow (3) $$ we read:

" ... ... If $$N^* \ne N$$, let $$x \in N - N^*$$.

Then $$N^* + xR$$ is a finitely generated submodule of N that properly contains $$N^*$$ ... ..."


My question is as follows:How does it follow from $$N^* \ne N$$ and $$x \in N - N^*$$ ... ...

... that ...

... ... $$N^* + xR$$ is a finitely generated submodule of N that properly contains $$N^*$$?
Hope someone can help ... ...

Peter***EDIT***

It is certainly the case that $$N^*$$ is finitely generated since it belongs to $$\mathscr{S}$$ and so it seems obvious that $$N^* + xR$$ is finitely generated ... but is it a submodule? Presumably it is a module because $$N^*$$ and $$xR$$ are modules and the sum of two modules is a module ... but how are we sure that it is a submodule of $$N$$ ...

It certainly also seems that $$N^* + xR$$ properly contains $$N^*$$ ...

... so I am really close to feeling I understand the answer to my question ...

Can someone please critique my thinking?
 
Last edited:
Physics news on Phys.org
It's a submodule of $N$ because $x$ is taken in $N$, actually $x\in N-N^{*}$
 

Similar threads

Replies
2
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 13 ·
Replies
13
Views
3K
  • · Replies 9 ·
Replies
9
Views
2K
Replies
2
Views
2K
Replies
4
Views
2K
  • · Replies 15 ·
Replies
15
Views
3K
  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K