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1. • CommentRowNumber1.
   • CommentAuthorUrs
   • CommentTimeSep 6th 2017
   • (edited Sep 6th 2017)
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   Author: Urs
   Format: MarkdownItexadded to _[[advanced and retarded propagator]]_ statement and proof of the expression $$ \Delta_R(x,y) \;=\; (2\pi)^{-(p+1)} \underset{\epsilon \to 0^+}{\lim} \int \frac{e^{-i k_\mu x^\mu}}{ k_\mu k^\mu + m^2 - i k_0 \epsilon/2 } d^4 k $$ ([this prop.](https://ncatlab.org/nlab/show/advanced+and+retarded+propagator#AdvancedPropagatorAsContourIntegral))

   added to advanced and retarded propagator statement and proof of the expression

   $$\Delta_R(x,y) \;=\; (2\pi)^{-(p+1)} \underset{\epsilon \to 0^+}{\lim} \int \frac{e^{-i k_\mu x^\mu}}{ k_\mu k^\mu + m^2 - i k_0 \epsilon/2 } d^4 k$$

   (this prop.)

2. • CommentRowNumber2.
   • CommentAuthorUrs
   • CommentTimeNov 14th 2017
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   Author: Urs
   Format: MarkdownItexThis needed some adjustment and fixing. I added in more precise background on the definition, and then an improved writeup of the computation: [here](https://ncatlab.org/nlab/show/advanced+and+retarded+causal+propagators#ForKleinGordonOperatorOnMinkowskiSpacetime).

   This needed some adjustment and fixing. I added in more precise background on the definition, and then an improved writeup of the computation: here.

3. • CommentRowNumber3.
   • CommentAuthorUrs
   • CommentTimeNov 20th 2017
   • (edited Nov 20th 2017)
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   Author: Urs
   Format: MarkdownItexI have further expanded the explicit computations in [that section](https://ncatlab.org/nlab/show/advanced+and+retarded+causal+propagators#ForKleinGordonOperatorOnMinkowskiSpacetime), now also of the causal propagator. I am copying this over to _[[causal propagator]]_, too. This means there is now much verbatim overlap between the entries _[[causal propagator]]_ and _[[advanced and retarded propagators]]_. It might make sense to just merge the two entries to one. But for the moment I keep them distinct.

   I have further expanded the explicit computations in that section, now also of the causal propagator. I am copying this over to causal propagator, too.

   This means there is now much verbatim overlap between the entries causal propagator and advanced and retarded propagators. It might make sense to just merge the two entries to one. But for the moment I keep them distinct.