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For questions about injective modules over a ring and injective objects in related categories.
1
vote
1
answer
405
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Question on simple modules and projective covers
I have the following question:
Let $A$ be an Artin algebra. Let $S_1$ and $S_2$ be simple modules in $\text{mod}(A)$ and let $P(S_1)$ be the projective cover of $S_1$. Let $f: P(S_1) \rightarrow S_2$ …
3
votes
2
answers
197
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Question on injective hulls
How can I show the following:
Let $f: M \rightarrow N$ be a morphism in $\text{mod}(A)$, where $A$ is an Artin algebra. Suppose $f \neq 0$. Then there exists a simple module $S$ with its injective h …
-1
votes
1
answer
141
views
infinite left degrees
I am reading a paper called A NOTE ON THE RADICAL OF A MODULE CATEGORY by
CLAUDIA CHAIO AND SHIPING LIU. This is a part of the paper:
Definition: Let $f: X \rightarrow Y$ be an irreducible morphism …
6
votes
1
answer
134
views
On the finiteness of an Auslander-Reiten component
I am reading a paper called A NOTE ON THE RADICAL OF A MODULE CATEGORY by
CLAUDIA CHAIO AND SHIPING LIU. This is Theorem 2.7:
And this is part of it's proof, in which the direction (2) $\Rightarrow $ …
1
vote
1
answer
194
views
About composition factors [closed]
I am reading a paper called A NOTE ON THE RADICAL OF A MODULE CATEGORY by
CLAUDIA CHAIO AND SHIPING LIU. This is part of the proof of Lemma 2.3
$A$ is assumed to be an Artin algebra and mod(A) the cat …
1
vote
1
answer
424
views
injective hull and projective cover of simple modules are indecomposable
Let $A$ be an Artinian algebra. Let $S$ be a simple module over $A$. Let $\pi: S \rightarrow I$ be the injective hull and $\tau: P \rightarrow S$ be the projective cover of $S$. Then $I$ and $P$ must …