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I am reading Dummit and Foote, Chapter 10, Section 10.5, Exact Sequences - Projective, Injective and Flat Modules.
I need help with a minor step of D&F, Chapter 10, Theorem 28 on liftings of homomorphisms.
In the proof of the first part of the theorem (see image below) D&F make the following statement:
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Conversely, if F is in the image of $$ \psi'$$ then $$ F = \psi' (F') $$ for some $$ F' \in Hom_R (D, L) $$ and so $$ \phi ( F (d) )) = \phi ( \psi ( F' (d))) $$ for any $$d \in D$$. ...
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My problem is that surely $$ F = \psi' (F') $$ implies that $$ \phi ( F (d) )) = \phi ( \psi' ( F' (d))) $$ and NOT $$ \phi ( F (d) )) = \phi ( \psi ( F' (d))) $$?
Hoping someone can help>
Theorem 28 and the first part of the proof read as follows:
https://www.physicsforums.com/attachments/2474
Peter
NOTE: This has also been posted on the Physics Forums in the forum Linear and Abstract Algebra.
I need help with a minor step of D&F, Chapter 10, Theorem 28 on liftings of homomorphisms.
In the proof of the first part of the theorem (see image below) D&F make the following statement:
-------------------------------------------------------------------------------
Conversely, if F is in the image of $$ \psi'$$ then $$ F = \psi' (F') $$ for some $$ F' \in Hom_R (D, L) $$ and so $$ \phi ( F (d) )) = \phi ( \psi ( F' (d))) $$ for any $$d \in D$$. ...
----------------------------------------------------------------------------
My problem is that surely $$ F = \psi' (F') $$ implies that $$ \phi ( F (d) )) = \phi ( \psi' ( F' (d))) $$ and NOT $$ \phi ( F (d) )) = \phi ( \psi ( F' (d))) $$?
Hoping someone can help>
Theorem 28 and the first part of the proof read as follows:
https://www.physicsforums.com/attachments/2474
Peter
NOTE: This has also been posted on the Physics Forums in the forum Linear and Abstract Algebra.
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