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Srednicki 9.17, 9.18

  1. Oct 15, 2009 #1
    Why is the expression 9.17 the sum of all diagrams with a single source removed?

    I thought diagrams stand for terms in double taylor expansion of Z_1(J).
  2. jcsd
  3. Oct 15, 2009 #2


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    The expression in 9.17 is

    [tex]{\delta\over\delta J(x)}Z_1(J)\Bigr|_{J=0}[/tex]

    The derivative with respect to J removes one factor of J, and then all other factors of J are set to zero. So the only surviving diagrams are those that had just one J to begin with.
  4. Oct 16, 2009 #3
    Thanks, Avodyne!

    Actually, when I stared at it again this morning, I already figured it out by myself.

    How come your such an expert on Srednick's book? Always when someone ask a question to his book, you give the answer right away. I remember you gave me great answers like one year back ago, which i have written as side notes in the book.
  5. Oct 16, 2009 #4


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    Srednicki had posted rough drafts of Spin Zero and Spin One Half at arxiv.org in 2004, and I thought they were much better than the existing textbooks, so by now I know the material pretty well.
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