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I am reading Dummit and Foote,, Section 15.4: Localization.
I am working on Proposition 38 - see attachment page 709 (also see attachment page 708 for definitions of \(\displaystyle ^eI \) and \(\displaystyle ^cJ \).
I am having some trouble proving the second part of Section (2), which D&F leave largely to the reader.
Proposition 38, Section 15.4, page 709 reads as follows:
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(2) For any ideal I of R we have
\(\displaystyle ^c{(^eI)} = \{ r \in R \ | \ dr \in I \) for some \(\displaystyle d \in D \} \)
Also \(\displaystyle ^eI = D^{-1}R \) if and only if \(\displaystyle I \cap D \ne \emptyset \)
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I can follow the proof of the first part of the above. However, for the proof of the second part - viz.:
\(\displaystyle ^eI = D^{-1}R \) if and only if \(\displaystyle I \cap D \ne \emptyset \)
D&F write "The second assertion of (2) then follows the definition of I' (where we have I' set equal to \(\displaystyle \{ r \in R \ | \ dr \in I \) for some \(\displaystyle d \in D \} \).
Can someone help me show (formally & rigorously) that \(\displaystyle ^eI = D^{-1}R \) if and only if \(\displaystyle I \cap D \ne \emptyset \) and thus help me to see how this follows easily from the definition of I'
Hope someone can help.
Peter
I am working on Proposition 38 - see attachment page 709 (also see attachment page 708 for definitions of \(\displaystyle ^eI \) and \(\displaystyle ^cJ \).
I am having some trouble proving the second part of Section (2), which D&F leave largely to the reader.
Proposition 38, Section 15.4, page 709 reads as follows:
-------------------------------------------------------------------------------
(2) For any ideal I of R we have
\(\displaystyle ^c{(^eI)} = \{ r \in R \ | \ dr \in I \) for some \(\displaystyle d \in D \} \)
Also \(\displaystyle ^eI = D^{-1}R \) if and only if \(\displaystyle I \cap D \ne \emptyset \)
----------------------------------------------------------------------------
I can follow the proof of the first part of the above. However, for the proof of the second part - viz.:
\(\displaystyle ^eI = D^{-1}R \) if and only if \(\displaystyle I \cap D \ne \emptyset \)
D&F write "The second assertion of (2) then follows the definition of I' (where we have I' set equal to \(\displaystyle \{ r \in R \ | \ dr \in I \) for some \(\displaystyle d \in D \} \).
Can someone help me show (formally & rigorously) that \(\displaystyle ^eI = D^{-1}R \) if and only if \(\displaystyle I \cap D \ne \emptyset \) and thus help me to see how this follows easily from the definition of I'
Hope someone can help.
Peter