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Idempotent Equivalence in Rings

  1. Feb 21, 2008 #1
    One of my books defines a relation which is "evidently" an equivalence relation. It says that two idempotents in a ring P and Q are said to be equivalent if there exist elements X and Y such that P = XY and Q = YX.

    The proof that this relation is transitive eludes me. There is so little information, that I feel like this has to have a really short proof, but I just can't seem to figure it out (or find it on the magical internet). If anyone can can ease my frustration, I would be grateful.
     
  2. jcsd
  3. Feb 21, 2008 #2

    gel

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    If P~Q and Q~R then, P=XY, Q=YX and Q=VW, R=WV.
    Then,
    P=P2=XYXY=XQY=(XV)(WY)
    R=R2=WVWV=WQV=(WY)(XV)
    so P~R.
     
  4. Feb 21, 2008 #3
    Alright that's about as complicated as I expected it to be...I basically had that written down, but apparently I don't quite have a fully functioning brain and for some reason couldn't see it. Many thanks.
     
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