- #1
Matthaeus
- 5
- 0
I am reading a nice book (Quarks and Leptons, by Halzen and Martin) about particle physics. It states that the general form of the propagator of a virtual particle is:
[tex]
\dfrac{i\sum_{\text{spins}}}{p^2 - m^2}
[/tex]
I see that this is the case for the Dirac propagator:
[tex]
\dfrac{i(\displaystyle{\not}{p} + m)}{p^2 - m^2} = \dfrac{i\sum_{s}u_s(p)\bar{u}_s(p)}{p^2 - m^2}
[/tex]
but how can I prove that always holds?
[tex]
\dfrac{i\sum_{\text{spins}}}{p^2 - m^2}
[/tex]
I see that this is the case for the Dirac propagator:
[tex]
\dfrac{i(\displaystyle{\not}{p} + m)}{p^2 - m^2} = \dfrac{i\sum_{s}u_s(p)\bar{u}_s(p)}{p^2 - m^2}
[/tex]
but how can I prove that always holds?