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Time ordering operator

  1. Dec 15, 2013 #1
  2. jcsd
  3. Dec 16, 2013 #2
    short answer: under the time ordering you can collect all of the U(τ) terms together and they cancel.
  4. Dec 16, 2013 #3
    How does that happen? The time ordering operator for τ>τ' has no effect on A(τ)B(τ') and reverses them in the case τ'>τ
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