Master Dissertation
Master Dissertation
Master Dissertation
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A ′ 2(x1, x2) = ˜ T1(x1)T1(x2) = −T1(x1)T1(x2)<br />
= e 2 γ µ<br />
abγν cd : ψa(x1)ψb(x1) :: ψc(x2)ψd(x2) : Aµ(x1)Aν(x2)<br />
<br />
: ψa(x1)ψb(x1)ψ c(x2)ψd(x2) :<br />
= e 2 γ µ<br />
ab γν cd<br />
= e 2 γ µ<br />
ab γν cd<br />
+ : ψ a(x1) | ψb(x1)ψ c(x2) | ψd(x2) :<br />
+ : | ψ a(x1)ψb(x1)ψ c(x2)ψd(x2) | :<br />
+ : | ψ a(x1) | ψb(x1)ψ c(x2) | ψd(x2) | :<br />
<br />
×<br />
<br />
: ψa(x1)ψb(x1)ψ c(x2)ψd(x2) :<br />
: Aµ(x1)Aν(x2) : + : | Aµ(x1)Aν(x2) | :<br />
+ 1<br />
i S(+)<br />
bc (x1 − x2) : ψa(x1)ψd(x2) :<br />
+ 1<br />
i S(−)<br />
da (x2 − x1) : ψb(x1)ψc(x2) :<br />
− S (+)<br />
bc (x1 − x2)S (−)<br />
da (x2<br />
<br />
− x1)<br />
<br />
×<br />
: Aµ(x1)Aν(x2) : +gµνiD (+)<br />
0 (x1 − x2)<br />
<br />
<br />
<br />
. (8.1)<br />
From (5.8) we see that the retarded distribution is given by (8.1) simply by<br />
substituting x1 ↔ x2. For convenience we also interchange the indices<br />
µ ↔ ν, a ↔ c and b ↔ d, arriving at<br />
R ′ 2(x1, x2) = T1(x2) ˜ T1(x1) = −T1(x2)T1(x1)<br />
<br />
: ψa(x1)ψb(x1)ψ c(x2)ψd(x2) :<br />
= e 2 γ µ<br />
ab γν cd<br />
− 1<br />
i S(+)<br />
da (x2 − x1) : ψb(x1)ψc(x2) :<br />
− 1<br />
i S(−)<br />
bc (x1 − x2) : ψa(x1)ψd(x2) :<br />
− S (+)<br />
da (x2 − x1)S (−)<br />
bc (x1<br />
<br />
− x2)<br />
<br />
×<br />
: Aµ(x1)Aν(x2) : +gµνiD (+)<br />
0 (x2 − x1)<br />
67<br />
<br />
. (8.2)